Contents
About ................................................................................................................................................................................... 1
Chapter 1: Getting started with Swift Language .......................................................................................... 2
Section 1.1: Your first Swift program ............................................................................................................................ 2
Section 1.2: Your first program in Swift on a Mac (using a Playground) ................................................................. 3
Section 1.3: Your first program in Swift Playgrounds app on iPad ........................................................................... 7
Section 1.4: Installing Swift ............................................................................................................................................ 8
Section 1.5: Optional Value and Optional enum ......................................................................................................... 8
Chapter 2: Variables & Properties ..................................................................................................................... 10
Section 2.1: Creating a Variable ................................................................................................................................. 10
Section 2.2: Property Observers ................................................................................................................................ 10
Section 2.3: Lazy Stored Properties ........................................................................................................................... 11
Section 2.4: Property Basics ....................................................................................................................................... 11
Section 2.5: Computed Properties ............................................................................................................................. 12
Section 2.6: Local and Global Variables ................................................................................................................... 12
Section 2.7: Type Properties ....................................................................................................................................... 13
Chapter 3: Numbers .................................................................................................................................................. 14
Section 3.1: Number types and literals ...................................................................................................................... 14
Section 3.2: Convert numbers to/from strings ........................................................................................................ 15
Section 3.3: Rounding .................................................................................................................................................. 15
Section 3.4: Random number generation ................................................................................................................. 16
Section 3.5: Convert one numeric type to another .................................................................................................. 17
Section 3.6: Exponentiation ........................................................................................................................................ 17
Chapter 4: Strings and Characters ................................................................................................................... 18
Section 4.1: String & Character Literals ..................................................................................................................... 18
Section 4.2: Concatenate strings ............................................................................................................................... 19
Section 4.3: String Encoding and Decomposition .................................................................................................... 20
Section 4.4: Examine and compare strings .............................................................................................................. 20
Section 4.5: Reversing Strings .................................................................................................................................... 21
Section 4.6: Check if String contains Characters from a Defined Set .................................................................... 21
Section 4.7: String Iteration ........................................................................................................................................ 22
Section 4.8: Splitting a String into an Array .............................................................................................................. 24
Section 4.9: Unicode .................................................................................................................................................... 24
Section 4.10: Converting Swift string to a number type .......................................................................................... 25
Section 4.11: Convert String to and from Data / NSData ........................................................................................ 25
Section 4.12: Formatting Strings ................................................................................................................................ 26
Section 4.13: Uppercase and Lowercase Strings ...................................................................................................... 26
Section 4.14: Remove characters from a string not defined in Set ........................................................................ 27
Section 4.15: Count occurrences of a Character into a String ................................................................................ 27
Section 4.16: Remove leading and trailing WhiteSpace and NewLine ................................................................... 27
Chapter 5: Booleans .................................................................................................................................................. 29
Section 5.1: What is Bool? ........................................................................................................................................... 29
Section 5.2: Booleans and Inline Conditionals .......................................................................................................... 29
Section 5.3: Boolean Logical Operators .................................................................................................................... 30
Section 5.4: Negate a Bool with the prefix ! operator .............................................................................................. 30
Chapter 6: Arrays ....................................................................................................................................................... 31
Section 6.1: Basics of Arrays ....................................................................................................................................... 31
Section 6.2: Extracting values of a given type from an Array with flatMap(_:) ................................................... 32
, Section 6.3: Combining an Array's elements with reduce(_:combine:) ................................................................. 32
Section 6.4: Flattening the result of an Array transformation with flatMap(_:) ................................................... 33
Section 6.5: Lazily flattening a multidimensional Array with flatten() ................................................................... 33
Section 6.6: Filtering out nil from an Array transformation with flatMap(_:) ....................................................... 34
Section 6.7: Subscripting an Array with a Range ..................................................................................................... 34
Section 6.8: Removing element from an array without knowing it's index ........................................................... 35
Section 6.9: Sorting an Array of Strings .................................................................................................................... 35
Section 6.10: Accessing indices safely ....................................................................................................................... 36
Section 6.11: Filtering an Array ................................................................................................................................... 37
Section 6.12: Transforming the elements of an Array with map(_:) ...................................................................... 37
Section 6.13: Useful Methods ...................................................................................................................................... 38
Section 6.14: Sorting an Array .................................................................................................................................... 38
Section 6.15: Finding the minimum or maximum element of an Array ................................................................. 39
Section 6.16: Modifying values in an array ............................................................................................................... 40
Section 6.17: Comparing 2 Arrays with zip ................................................................................................................ 40
Section 6.18: Grouping Array values .......................................................................................................................... 41
Section 6.19: Value Semantics .................................................................................................................................... 42
Section 6.20: Accessing Array Values ....................................................................................................................... 42
Chapter 7: Tuples ........................................................................................................................................................ 44
Section 7.1: What are Tuples? .................................................................................................................................... 44
Section 7.2: Decomposing into individual variables ................................................................................................ 44
Section 7.3: Tuples as the Return Value of Functions ............................................................................................. 45
Section 7.4: Using a typealias to name your tuple type ......................................................................................... 45
Section 7.5: Swapping values ..................................................................................................................................... 46
Section 7.6: Tuples as Case in Switch ........................................................................................................................ 46
Chapter 8: Enums ....................................................................................................................................................... 48
Section 8.1: Basic enumerations ................................................................................................................................. 48
Section 8.2: Enums with associated values .............................................................................................................. 48
Section 8.3: Indirect payloads .................................................................................................................................... 49
Section 8.4: Raw and Hash values ............................................................................................................................ 50
Section 8.5: Initializers ................................................................................................................................................. 51
Section 8.6: Enumerations share many features with classes and structures ..................................................... 52
Section 8.7: Nested Enumerations ............................................................................................................................. 53
Chapter 9: Structs ...................................................................................................................................................... 54
Section 9.1: Structs are value types ........................................................................................................................... 54
Section 9.2: Accessing members of struct ................................................................................................................ 54
Section 9.3: Basics of Structs ..................................................................................................................................... 54
Section 9.4: Mutating a Struct .................................................................................................................................... 55
Section 9.5: Structs cannot inherit ............................................................................................................................. 55
Chapter 10: Sets ........................................................................................................................................................... 57
Section 10.1: Declaring Sets ........................................................................................................................................ 57
Section 10.2: Performing operations on sets ............................................................................................................ 57
Section 10.3: CountedSet ............................................................................................................................................. 58
Section 10.4: Modifying values in a set ...................................................................................................................... 58
Section 10.5: Checking whether a set contains a value ........................................................................................... 58
Section 10.6: Adding values of my own type to a Set .............................................................................................. 58
Chapter 11: Dictionaries ........................................................................................................................................... 60
Section 11.1: Declaring Dictionaries ............................................................................................................................ 60
Section 11.2: Accessing Values .................................................................................................................................... 60
Section 11.3: Change Value of Dictionary using Key ................................................................................................ 61
, Section 11.4: Get all keys in Dictionary ....................................................................................................................... 61
Section 11.5: Modifying Dictionaries ........................................................................................................................... 61
Section 11.6: Merge two dictionaries .......................................................................................................................... 62
Chapter 12: Switch ...................................................................................................................................................... 63
Section 12.1: Switch and Optionals ............................................................................................................................. 63
Section 12.2: Basic Use ................................................................................................................................................ 63
Section 12.3: Matching a Range ................................................................................................................................. 63
Section 12.4: Partial matching .................................................................................................................................... 64
Section 12.5: Using the where statement in a switch ............................................................................................... 65
Section 12.6: Matching Multiple Values ...................................................................................................................... 65
Section 12.7: Switch and Enums ................................................................................................................................. 66
Section 12.8: Switches and tuples .............................................................................................................................. 66
Section 12.9: Satisfy one of multiple constraints using switch ................................................................................ 67
Section 12.10: Matching based on class - great for prepareForSegue .................................................................. 67
Section 12.11: Switch fallthroughs ............................................................................................................................... 68
Chapter 13: Optionals ................................................................................................................................................ 69
Section 13.1: Types of Optionals ................................................................................................................................. 69
Section 13.2: Unwrapping an Optional ...................................................................................................................... 69
Section 13.3: Nil Coalescing Operator ........................................................................................................................ 71
Section 13.4: Optional Chaining .................................................................................................................................. 71
Section 13.5: Overview - Why Optionals? .................................................................................................................. 72
Chapter 14: Conditionals ......................................................................................................................................... 74
Section 14.1: Optional binding and "where" clauses ................................................................................................. 74
Section 14.2: Using Guard ........................................................................................................................................... 75
Section 14.3: Basic conditionals: if-statements ......................................................................................................... 75
Section 14.4: Ternary operator ................................................................................................................................... 76
Section 14.5: Nil-Coalescing Operator ....................................................................................................................... 77
Chapter 15: Error Handling .................................................................................................................................... 78
Section 15.1: Error handling basics ............................................................................................................................. 78
Section 15.2: Catching dierent error types ............................................................................................................. 79
Section 15.3: Catch and Switch Pattern for Explicit Error Handling ........................................................................ 80
Section 15.4: Disabling Error Propagation ................................................................................................................ 81
Section 15.5: Create custom Error with localized description ................................................................................. 81
Chapter 16: Loops ....................................................................................................................................................... 83
Section 16.1: For-in loop ............................................................................................................................................... 83
Section 16.2: Repeat-while loop ................................................................................................................................. 85
Section 16.3: For-in loop with filtering ........................................................................................................................ 85
Section 16.4: Sequence Type forEach block ............................................................................................................. 86
Section 16.5: while loop ............................................................................................................................................... 86
Section 16.6: Breaking a loop ..................................................................................................................................... 87
Chapter 17: Protocols ................................................................................................................................................ 88
Section 17.1: Protocol Basics ....................................................................................................................................... 88
Section 17.2: Delegate pattern ................................................................................................................................... 90
Section 17.3: Associated type requirements ............................................................................................................. 91
Section 17.4: Class-Only Protocols ............................................................................................................................. 93
Section 17.5: Protocol extension for a specific conforming class ........................................................................... 94
Section 17.6: Using the RawRepresentable protocol (Extensible Enum) ............................................................... 94
Section 17.7: Implementing Hashable protocol ........................................................................................................ 95
Chapter 18: Functions ............................................................................................................................................... 97
, Section 18.1: Basic Use ................................................................................................................................................. 97
Section 18.2: Functions with Parameters ................................................................................................................... 97
Section 18.3: Subscripts ............................................................................................................................................... 98
Section 18.4: Methods .................................................................................................................................................. 99
Section 18.5: Variadic Parameters ........................................................................................................................... 100
Section 18.6: Operators are Functions .................................................................................................................... 100
Section 18.7: Passing and returning functions ........................................................................................................ 101
Section 18.8: Function types ..................................................................................................................................... 101
Section 18.9: Inout Parameters ................................................................................................................................ 101
Section 18.10: Throwing Errors ................................................................................................................................. 101
Section 18.11: Returning Values ................................................................................................................................ 102
Section 18.12: Trailing Closure Syntax ..................................................................................................................... 102
Section 18.13: Functions With Closures .................................................................................................................... 103
Chapter 19: Extensions ........................................................................................................................................... 105
Section 19.1: What are Extensions? .......................................................................................................................... 105
Section 19.2: Variables and functions ...................................................................................................................... 105
Section 19.3: Initializers in Extensions ...................................................................................................................... 106
Section 19.4: Subscripts ............................................................................................................................................. 106
Section 19.5: Protocol extensions ............................................................................................................................. 106
Section 19.6: Restrictions .......................................................................................................................................... 107
Section 19.7: What are extensions and when to use them .................................................................................... 107
Chapter 20: Classes ................................................................................................................................................. 109
Section 20.1: Defining a Class .................................................................................................................................. 109
Section 20.2: Properties and Methods .................................................................................................................... 109
Section 20.3: Reference Semantics ......................................................................................................................... 109
Section 20.4: Classes and Multiple Inheritance ...................................................................................................... 110
Section 20.5: deinit .................................................................................................................................................... 111
Chapter 21: Type Casting ...................................................................................................................................... 112
Section 21.1: Downcasting ......................................................................................................................................... 112
Section 21.2: Type casting in Swift Language ........................................................................................................ 112
Section 21.3: Upcasting ............................................................................................................................................. 114
Section 21.4: Example of using a downcast on a function parameter involving subclassing ........................... 114
Section 21.5: Casting with switch .............................................................................................................................. 115
Chapter 22: Generics ............................................................................................................................................... 116
Section 22.1: The Basics of Generics ....................................................................................................................... 116
Section 22.2: Constraining Generic Placeholder Types ........................................................................................ 117
Section 22.3: Generic Class Examples ..................................................................................................................... 118
Section 22.4: Using Generics to Simplify Array Functions .................................................................................... 119
Section 22.5: Advanced Type Constraints .............................................................................................................. 119
Section 22.6: Generic Class Inheritance .................................................................................................................. 120
Section 22.7: Use generics to enhance type-safety .............................................................................................. 121
Chapter 23: OptionSet ............................................................................................................................................ 122
Section 23.1: OptionSet Protocol .............................................................................................................................. 122
Chapter 24: Reading & Writing JSON ............................................................................................................ 123
Section 24.1: JSON Serialization, Encoding, and Decoding with Apple Foundation and the Swift Standard
Library ................................................................................................................................................................ 123
Section 24.2: SwiftyJSON ......................................................................................................................................... 126
Section 24.3: Freddy ................................................................................................................................................. 127
Section 24.4: JSON Parsing Swift 3 ......................................................................................................................... 129
Section 24.5: Simple JSON parsing into custom objects ...................................................................................... 131
About ................................................................................................................................................................................... 1
Chapter 1: Getting started with Swift Language .......................................................................................... 2
Section 1.1: Your first Swift program ............................................................................................................................ 2
Section 1.2: Your first program in Swift on a Mac (using a Playground) ................................................................. 3
Section 1.3: Your first program in Swift Playgrounds app on iPad ........................................................................... 7
Section 1.4: Installing Swift ............................................................................................................................................ 8
Section 1.5: Optional Value and Optional enum ......................................................................................................... 8
Chapter 2: Variables & Properties ..................................................................................................................... 10
Section 2.1: Creating a Variable ................................................................................................................................. 10
Section 2.2: Property Observers ................................................................................................................................ 10
Section 2.3: Lazy Stored Properties ........................................................................................................................... 11
Section 2.4: Property Basics ....................................................................................................................................... 11
Section 2.5: Computed Properties ............................................................................................................................. 12
Section 2.6: Local and Global Variables ................................................................................................................... 12
Section 2.7: Type Properties ....................................................................................................................................... 13
Chapter 3: Numbers .................................................................................................................................................. 14
Section 3.1: Number types and literals ...................................................................................................................... 14
Section 3.2: Convert numbers to/from strings ........................................................................................................ 15
Section 3.3: Rounding .................................................................................................................................................. 15
Section 3.4: Random number generation ................................................................................................................. 16
Section 3.5: Convert one numeric type to another .................................................................................................. 17
Section 3.6: Exponentiation ........................................................................................................................................ 17
Chapter 4: Strings and Characters ................................................................................................................... 18
Section 4.1: String & Character Literals ..................................................................................................................... 18
Section 4.2: Concatenate strings ............................................................................................................................... 19
Section 4.3: String Encoding and Decomposition .................................................................................................... 20
Section 4.4: Examine and compare strings .............................................................................................................. 20
Section 4.5: Reversing Strings .................................................................................................................................... 21
Section 4.6: Check if String contains Characters from a Defined Set .................................................................... 21
Section 4.7: String Iteration ........................................................................................................................................ 22
Section 4.8: Splitting a String into an Array .............................................................................................................. 24
Section 4.9: Unicode .................................................................................................................................................... 24
Section 4.10: Converting Swift string to a number type .......................................................................................... 25
Section 4.11: Convert String to and from Data / NSData ........................................................................................ 25
Section 4.12: Formatting Strings ................................................................................................................................ 26
Section 4.13: Uppercase and Lowercase Strings ...................................................................................................... 26
Section 4.14: Remove characters from a string not defined in Set ........................................................................ 27
Section 4.15: Count occurrences of a Character into a String ................................................................................ 27
Section 4.16: Remove leading and trailing WhiteSpace and NewLine ................................................................... 27
Chapter 5: Booleans .................................................................................................................................................. 29
Section 5.1: What is Bool? ........................................................................................................................................... 29
Section 5.2: Booleans and Inline Conditionals .......................................................................................................... 29
Section 5.3: Boolean Logical Operators .................................................................................................................... 30
Section 5.4: Negate a Bool with the prefix ! operator .............................................................................................. 30
Chapter 6: Arrays ....................................................................................................................................................... 31
Section 6.1: Basics of Arrays ....................................................................................................................................... 31
Section 6.2: Extracting values of a given type from an Array with flatMap(_:) ................................................... 32
, Section 6.3: Combining an Array's elements with reduce(_:combine:) ................................................................. 32
Section 6.4: Flattening the result of an Array transformation with flatMap(_:) ................................................... 33
Section 6.5: Lazily flattening a multidimensional Array with flatten() ................................................................... 33
Section 6.6: Filtering out nil from an Array transformation with flatMap(_:) ....................................................... 34
Section 6.7: Subscripting an Array with a Range ..................................................................................................... 34
Section 6.8: Removing element from an array without knowing it's index ........................................................... 35
Section 6.9: Sorting an Array of Strings .................................................................................................................... 35
Section 6.10: Accessing indices safely ....................................................................................................................... 36
Section 6.11: Filtering an Array ................................................................................................................................... 37
Section 6.12: Transforming the elements of an Array with map(_:) ...................................................................... 37
Section 6.13: Useful Methods ...................................................................................................................................... 38
Section 6.14: Sorting an Array .................................................................................................................................... 38
Section 6.15: Finding the minimum or maximum element of an Array ................................................................. 39
Section 6.16: Modifying values in an array ............................................................................................................... 40
Section 6.17: Comparing 2 Arrays with zip ................................................................................................................ 40
Section 6.18: Grouping Array values .......................................................................................................................... 41
Section 6.19: Value Semantics .................................................................................................................................... 42
Section 6.20: Accessing Array Values ....................................................................................................................... 42
Chapter 7: Tuples ........................................................................................................................................................ 44
Section 7.1: What are Tuples? .................................................................................................................................... 44
Section 7.2: Decomposing into individual variables ................................................................................................ 44
Section 7.3: Tuples as the Return Value of Functions ............................................................................................. 45
Section 7.4: Using a typealias to name your tuple type ......................................................................................... 45
Section 7.5: Swapping values ..................................................................................................................................... 46
Section 7.6: Tuples as Case in Switch ........................................................................................................................ 46
Chapter 8: Enums ....................................................................................................................................................... 48
Section 8.1: Basic enumerations ................................................................................................................................. 48
Section 8.2: Enums with associated values .............................................................................................................. 48
Section 8.3: Indirect payloads .................................................................................................................................... 49
Section 8.4: Raw and Hash values ............................................................................................................................ 50
Section 8.5: Initializers ................................................................................................................................................. 51
Section 8.6: Enumerations share many features with classes and structures ..................................................... 52
Section 8.7: Nested Enumerations ............................................................................................................................. 53
Chapter 9: Structs ...................................................................................................................................................... 54
Section 9.1: Structs are value types ........................................................................................................................... 54
Section 9.2: Accessing members of struct ................................................................................................................ 54
Section 9.3: Basics of Structs ..................................................................................................................................... 54
Section 9.4: Mutating a Struct .................................................................................................................................... 55
Section 9.5: Structs cannot inherit ............................................................................................................................. 55
Chapter 10: Sets ........................................................................................................................................................... 57
Section 10.1: Declaring Sets ........................................................................................................................................ 57
Section 10.2: Performing operations on sets ............................................................................................................ 57
Section 10.3: CountedSet ............................................................................................................................................. 58
Section 10.4: Modifying values in a set ...................................................................................................................... 58
Section 10.5: Checking whether a set contains a value ........................................................................................... 58
Section 10.6: Adding values of my own type to a Set .............................................................................................. 58
Chapter 11: Dictionaries ........................................................................................................................................... 60
Section 11.1: Declaring Dictionaries ............................................................................................................................ 60
Section 11.2: Accessing Values .................................................................................................................................... 60
Section 11.3: Change Value of Dictionary using Key ................................................................................................ 61
, Section 11.4: Get all keys in Dictionary ....................................................................................................................... 61
Section 11.5: Modifying Dictionaries ........................................................................................................................... 61
Section 11.6: Merge two dictionaries .......................................................................................................................... 62
Chapter 12: Switch ...................................................................................................................................................... 63
Section 12.1: Switch and Optionals ............................................................................................................................. 63
Section 12.2: Basic Use ................................................................................................................................................ 63
Section 12.3: Matching a Range ................................................................................................................................. 63
Section 12.4: Partial matching .................................................................................................................................... 64
Section 12.5: Using the where statement in a switch ............................................................................................... 65
Section 12.6: Matching Multiple Values ...................................................................................................................... 65
Section 12.7: Switch and Enums ................................................................................................................................. 66
Section 12.8: Switches and tuples .............................................................................................................................. 66
Section 12.9: Satisfy one of multiple constraints using switch ................................................................................ 67
Section 12.10: Matching based on class - great for prepareForSegue .................................................................. 67
Section 12.11: Switch fallthroughs ............................................................................................................................... 68
Chapter 13: Optionals ................................................................................................................................................ 69
Section 13.1: Types of Optionals ................................................................................................................................. 69
Section 13.2: Unwrapping an Optional ...................................................................................................................... 69
Section 13.3: Nil Coalescing Operator ........................................................................................................................ 71
Section 13.4: Optional Chaining .................................................................................................................................. 71
Section 13.5: Overview - Why Optionals? .................................................................................................................. 72
Chapter 14: Conditionals ......................................................................................................................................... 74
Section 14.1: Optional binding and "where" clauses ................................................................................................. 74
Section 14.2: Using Guard ........................................................................................................................................... 75
Section 14.3: Basic conditionals: if-statements ......................................................................................................... 75
Section 14.4: Ternary operator ................................................................................................................................... 76
Section 14.5: Nil-Coalescing Operator ....................................................................................................................... 77
Chapter 15: Error Handling .................................................................................................................................... 78
Section 15.1: Error handling basics ............................................................................................................................. 78
Section 15.2: Catching dierent error types ............................................................................................................. 79
Section 15.3: Catch and Switch Pattern for Explicit Error Handling ........................................................................ 80
Section 15.4: Disabling Error Propagation ................................................................................................................ 81
Section 15.5: Create custom Error with localized description ................................................................................. 81
Chapter 16: Loops ....................................................................................................................................................... 83
Section 16.1: For-in loop ............................................................................................................................................... 83
Section 16.2: Repeat-while loop ................................................................................................................................. 85
Section 16.3: For-in loop with filtering ........................................................................................................................ 85
Section 16.4: Sequence Type forEach block ............................................................................................................. 86
Section 16.5: while loop ............................................................................................................................................... 86
Section 16.6: Breaking a loop ..................................................................................................................................... 87
Chapter 17: Protocols ................................................................................................................................................ 88
Section 17.1: Protocol Basics ....................................................................................................................................... 88
Section 17.2: Delegate pattern ................................................................................................................................... 90
Section 17.3: Associated type requirements ............................................................................................................. 91
Section 17.4: Class-Only Protocols ............................................................................................................................. 93
Section 17.5: Protocol extension for a specific conforming class ........................................................................... 94
Section 17.6: Using the RawRepresentable protocol (Extensible Enum) ............................................................... 94
Section 17.7: Implementing Hashable protocol ........................................................................................................ 95
Chapter 18: Functions ............................................................................................................................................... 97
, Section 18.1: Basic Use ................................................................................................................................................. 97
Section 18.2: Functions with Parameters ................................................................................................................... 97
Section 18.3: Subscripts ............................................................................................................................................... 98
Section 18.4: Methods .................................................................................................................................................. 99
Section 18.5: Variadic Parameters ........................................................................................................................... 100
Section 18.6: Operators are Functions .................................................................................................................... 100
Section 18.7: Passing and returning functions ........................................................................................................ 101
Section 18.8: Function types ..................................................................................................................................... 101
Section 18.9: Inout Parameters ................................................................................................................................ 101
Section 18.10: Throwing Errors ................................................................................................................................. 101
Section 18.11: Returning Values ................................................................................................................................ 102
Section 18.12: Trailing Closure Syntax ..................................................................................................................... 102
Section 18.13: Functions With Closures .................................................................................................................... 103
Chapter 19: Extensions ........................................................................................................................................... 105
Section 19.1: What are Extensions? .......................................................................................................................... 105
Section 19.2: Variables and functions ...................................................................................................................... 105
Section 19.3: Initializers in Extensions ...................................................................................................................... 106
Section 19.4: Subscripts ............................................................................................................................................. 106
Section 19.5: Protocol extensions ............................................................................................................................. 106
Section 19.6: Restrictions .......................................................................................................................................... 107
Section 19.7: What are extensions and when to use them .................................................................................... 107
Chapter 20: Classes ................................................................................................................................................. 109
Section 20.1: Defining a Class .................................................................................................................................. 109
Section 20.2: Properties and Methods .................................................................................................................... 109
Section 20.3: Reference Semantics ......................................................................................................................... 109
Section 20.4: Classes and Multiple Inheritance ...................................................................................................... 110
Section 20.5: deinit .................................................................................................................................................... 111
Chapter 21: Type Casting ...................................................................................................................................... 112
Section 21.1: Downcasting ......................................................................................................................................... 112
Section 21.2: Type casting in Swift Language ........................................................................................................ 112
Section 21.3: Upcasting ............................................................................................................................................. 114
Section 21.4: Example of using a downcast on a function parameter involving subclassing ........................... 114
Section 21.5: Casting with switch .............................................................................................................................. 115
Chapter 22: Generics ............................................................................................................................................... 116
Section 22.1: The Basics of Generics ....................................................................................................................... 116
Section 22.2: Constraining Generic Placeholder Types ........................................................................................ 117
Section 22.3: Generic Class Examples ..................................................................................................................... 118
Section 22.4: Using Generics to Simplify Array Functions .................................................................................... 119
Section 22.5: Advanced Type Constraints .............................................................................................................. 119
Section 22.6: Generic Class Inheritance .................................................................................................................. 120
Section 22.7: Use generics to enhance type-safety .............................................................................................. 121
Chapter 23: OptionSet ............................................................................................................................................ 122
Section 23.1: OptionSet Protocol .............................................................................................................................. 122
Chapter 24: Reading & Writing JSON ............................................................................................................ 123
Section 24.1: JSON Serialization, Encoding, and Decoding with Apple Foundation and the Swift Standard
Library ................................................................................................................................................................ 123
Section 24.2: SwiftyJSON ......................................................................................................................................... 126
Section 24.3: Freddy ................................................................................................................................................. 127
Section 24.4: JSON Parsing Swift 3 ......................................................................................................................... 129
Section 24.5: Simple JSON parsing into custom objects ...................................................................................... 131
