book

Swift

Name: Swift
ISBN: 9781807783877

by Rheinwerk Publishing, Inc, Kerem Koseoglu

April 2026

Intermediate

683 pages

25h 29m

English

Packt Publishing

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Notes on Usage
Dedication
1 Introduction
1.1 About this Book
1.2 Welcome to Swift!
1.3 Why Learn Swift?
1.4 Swift Versus Other Programming Languages
1.4.1 Python1.4.2 Java1.4.3 C#1.4.4 JavaScript1.4.5 Dart1.4.6 Kotlin1.4.7 C++1.4.8 Rust1.4.9 Picking the Ideal Language
1.5 Setting Up the Development Environment
1.5.1 Preparing Your Mac1.5.2 Alternative Options for Swift Development
1.6 Summary
2 Variables
2.1 Variables2.1.1 About Variables and Constants2.1.2 Declaring Simple Variables and Constants2.1.3 Type Annotations2.1.4 Comments
2.2 Boolean
2.2.1 About Booleans2.2.2 AND Operator2.2.3 OR Operator2.2.4 Nested Conditions

2.3 Numbers
2.3.1 Numeric Types2.3.2 Arithmetic Operators2.3.3 Comparison Operators2.3.4 Numeric Literals
2.4 Text
2.4.1 About Strings2.4.2 Basic String Literals2.4.3 Multiline String Literals2.4.4 Escape Sequences2.4.5 Concatenation2.4.6 String Interpolation2.4.7 Checking String Contents2.4.8 Substrings2.4.9 Modifying Strings2.4.10 Comparison Operators2.4.11 String/Number Conversion2.4.12 Regular Expressions
2.5 Dates and Times
2.5.1 Basic Data Types2.5.2 Arithmetic Operations2.5.3 Comparison2.5.4 Measuring Durations2.5.5 String/Date Conversion2.5.6 Internationalization
2.6 Quantities
2.6.1 Units2.6.2 Measurement2.6.3 Unit Conversions2.6.4 Arithmetic Operations
2.7 Tuples
2.7.1 Basic Tuples2.7.2 Named Tuples2.7.3 Tuple Type Annotations2.7.4 Comparison
2.8 Type Aliases
2.8.1 Basic Types2.8.2 Complex Types
2.9 Summary
3 Collections
3.1 Arrays3.1.1 Creating Arrays3.1.2 Arrays as Constants3.1.3 Accessing Arrays3.1.4 Array Derivation3.1.5 Modifying Arrays3.1.6 Iterating Through Arrays
3.2 Sets
3.2.1 Creating Sets3.2.2 Sets as Constants3.2.3 Accessing Sets3.2.4 Set Derivation3.2.5 Checking for Supersets3.2.6 Modifying Sets3.2.7 Iterating Through Sets
3.3 Dictionaries
3.3.1 Creating Dictionaries3.3.2 Dictionaries as Constants3.3.3 Accessing Dictionaries3.3.4 Modifying Dictionaries3.3.5 Iterating Through a Dictionary
3.4 Summary
4 Control Flow
4.1 Conditional Statements4.1.1 If-Else4.1.2 Logical Operators4.1.3 Ternary Operator4.1.4 Nil-Coalescing Operator4.1.5 Switch
4.2 Loops
4.2.1 For-In Loops4.2.2 While Loops4.2.3 Repeat-While Loops
4.3 Control Transfer Statements
4.3.1 Break4.3.2 Continue4.3.3 Fallthrough4.3.4 Guard
4.4 Summary
5 Functions
5.1 What Is a Function?
5.2 Defining and Calling Functions
5.2.1 Defining a Function5.2.2 Calling a Function from the Program5.2.3 Calling a Function from Another Function5.2.4 Variable Scope in Functions
5.3 Input Parameters
5.3.1 Named Parameters5.3.2 Omitting Argument Labels5.3.3 Default Arguments5.3.4 Guarding Functions
5.4 Returning Values
5.4.1 Returning Single Values5.4.2 Returning Multiple Values
5.5 Variadic Parameters
5.6 Function Overloading
5.7 Inout Parameters
5.8 Nested Functions
5.9 Function Types
5.9.1 Basic5.9.2 Function Types as Parameter Types5.9.3 Function Types as Return Types
5.10 Closures
5.10.1 Closure Expressions5.10.2 Trailing Closures5.10.3 Escaping Closures5.10.4 Autoclosures
5.11 Generic Functions
5.11.1 Generic Functions5.11.2 Type Constraints5.11.3 Generic Where Clauses
5.12 Summary
6 Optionals
6.1 What Are Optionals?6.1.1 Tuple Optionals6.1.2 Simple Variable Optionals6.1.3 Collection Optionals6.1.4 Function Optionals
6.2 Optional Binding
6.3 Implicitly Unwrapped Optionals
6.4 Optional Chaining
6.5 Summary
7 Enumerations
7.1 What Are Enumerations?
7.2 Declaring Enumerations
7.2.1 Case Values7.2.2 Raw Values7.2.3 Associated Values
7.3 Computed Properties
7.4 Functions in Enumerations
7.5 Iterating over Enumerations
7.5.1 Iterating over Case Values7.5.2 Iterating over Raw Values7.5.3 Iterating over Associated Values
7.6 Recursive Enumerations
7.7 Generic Enumerations
7.8 Summary
8 Structs
8.1 What Is a Struct?
8.2 Declaring Structs
8.2.1 Basic Struct Declaration8.2.2 Mutable Properties8.2.3 Complex Properties8.2.4 Nested Structs8.2.5 Default Property Values8.2.6 Optional Properties
8.3 Static Properties
8.4 Computed Properties
8.4.1 Getters8.4.2 Setters
8.5 Functions
8.5.1 Initialization8.5.2 Nonmutating Functions8.5.3 Mutating Functions8.5.4 Static Functions
8.6 Encapsulation
8.6.1 Private Properties8.6.2 Private Functions
8.7 Structs as Function Parameters
8.8 Generic Structs
8.9 Advanced Features
8.9.1 Lazy Properties8.9.2 Property Observers8.9.3 Property Wrappers8.9.4 Subscripts8.9.5 Failable Initialization
8.10 Summary
9 Classes
9.1 Declaring Classes9.1.1 Basic Class Declaration9.1.2 Reference Semantics9.1.3 Composition
9.2 Functions
9.2.1 Mutability9.2.2 Deinitialization9.2.3 Convenience Initialization
9.3 Inheritance
9.3.1 Superclasses and Subclasses9.3.2 Overriding Functions9.3.3 Overriding Initializers9.3.4 Overriding Computed Properties9.3.5 Overriding Subscripts9.3.6 Casting9.3.7 AnyObject Type
9.4 Classes as Function Parameters
9.5 Memory Management
9.5.1 Strong References9.5.2 Weak References9.5.3 Unowned References
9.6 Summary
10 Protocols
10.1 Purpose of Protocols
10.2 Function Requirements
10.2.1 Nonmutating Function10.2.2 Mutating Function10.2.3 Static Function
10.3 Initializer Requirements
10.4 Property Requirements
10.4.1 Get Requirement10.4.2 Get Set Requirement10.4.3 Static Requirement
10.5 Implementing Multiple Protocols
10.6 Checking for Protocol Conformance
10.7 Protocols as Function Parameters
10.7.1 Protocol Type10.7.2 Existential Type10.7.3 Opaque Type
10.8 Associated Types
10.9 Using Standard Protocols
10.9.1 Equatable10.9.2 Comparable10.9.3 Identifiable10.9.4 Hashable10.9.5 CustomStringConvertible
10.10 Summary
11 Extensions
11.1 Extending Enumerations
11.2 Extending Structs
11.3 Extending Classes
11.4 Extending Protocols
11.5 Operator Extensions
11.5.1 Arithmetic and Boolean Operators11.5.2 Equality and Comparison Operators11.5.3 Prefix and Postfix Operators11.5.4 Custom Operators
11.6 Extending Swift Data Types
11.6.1 Sample Usage11.6.2 Avoiding Name Conflicts
11.7 Generic Extensions
11.8 Summary
12 Error Handling
12.1 Understanding Errors in Swift
12.2 Throwing Errors
12.2.1 Throwing Built-in Errors12.2.2 Throwing Custom Errors12.2.3 Propagating Errors
12.3 Catching Errors
12.3.1 Direct Pattern Matching12.3.2 Error Pattern Matching12.3.3 Localized Error Messages12.3.4 Optional Try
12.4 Cleanup with Defer
12.5 Runtime Checks
12.5.1 Debug Runtime Checks12.5.2 Release Runtime Checks
12.6 Summary
13 File Handling
13.1 Text Files13.1.1 Reading Text Files13.1.2 Writing Text Files
13.2 Binary Files
13.2.1 Reading Binary Files13.2.2 Writing Binary Files
13.3 Working with Common Formats
13.3.1 JSON13.3.2 Property List
13.4 File System Operations
13.4.1 Examining Folders13.4.2 Manipulating Folders13.4.3 Examining Files13.4.4 Manipulating Files
13.5 Summary
14 Concurrency
14.1 What Is Concurrency?
14.2 Async Functions
14.2.1 Writing Async Functions14.2.2 Calling Async Functions14.2.3 Running Functions in Parallel
14.3 Tasks
14.3.1 Creating Tasks14.3.2 Task Groups14.3.3 Task Priorities14.3.4 Task Cancellation
14.4 Async Streams
14.4.1 Starting an Async Stream14.4.2 Canceling an Async Stream14.4.3 Handling Async Stream Errors
14.5 Shared State Safety
14.5.1 Task-Local Values14.5.2 Detached Tasks14.5.3 Actors14.5.4 Sendable Types
14.6 Summary
15 Modules in Swift
15.1 Introduction to Modules15.1.1 What Is a Module?15.1.2 Why Use Modules?
15.2 Working with Frameworks
15.2.1 Setting Up a New Framework15.2.2 Adding Code to a Framework15.2.3 Building a Framework15.2.4 Importing a Framework
15.3 Working with Packages
15.3.1 Setting Up a New Package15.3.2 Adding Code to a Package15.3.3 Importing a Package
15.4 Access Control
15.4.1 Open15.4.2 Public15.4.3 Internal15.4.4 File Private15.4.5 Private
15.5 Summary
16 Conclusion
A Unit Testing
A.1 Introduction to Unit TestingA.1.1 What Is a Unit Test?A.1.2 Test-Driven DevelopmentA.1.3 Unit Testing in Swift
A.2 Unit Testing with XCTest
A.2.1 Preparing a Testable ProjectA.2.2 Coding Unit TestsA.2.3 Executing Unit TestsA.2.4 AssertionsA.2.5 Test Coverage
A.3 Unit Testing with Swift Testing
A.3.1 Preparing a Testable ProjectA.3.2 Coding Unit TestsA.3.3 Executing Unit TestsA.3.4 Test MacrosA.3.5 Test Coverage
A.4 Summary
B Debugging
B.1 Debugging in XcodeB.1.1 Creating a Sample ProjectB.1.2 Setting BreakpointsB.1.3 Starting a Debug SessionB.1.4 Running Through a DebugB.1.5 Changing Breakpoints During Debug
B.2 Advanced Debugging Tools
B.2.1 Conditional BreakpointsB.2.2 Symbolic BreakpointsB.2.3 Performance Debugging
B.3 Support Commands
B.4 Summary
The Author
Index
Service Pages
Legal Notes

Content preview from Swift

6 Optionals

Optionals are a signature feature of the Swift language, through which the possibility of a variable having an empty value is managed via simple operators.

Swift’s optionals provide a type-safe way to handle the presence or absence of a value. They prevent unsafe access to null values, which might otherwise crash an app easily. Optionals are simple and easy to learn, but they are one of the cornerstones of Swift’s safety features.

In this chapter, you will learn about optionals, their syntaxes, and their features via sensible examples—as usual.

6.1 What Are Optionals?

In previous chapters, we went over many topics dealing with values. You know by now that variables and collections can hold values, while functions can import, calculate, ...

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ISBN: 9781807783877

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Swift

by Rheinwerk Publishing, Inc, Kerem Koseoglu

6 Optionals

6.1 What Are Optionals?

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