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Learning Swift Second Edition

Learning Swift Second Edition

By : Andrew J Wagner
5 (1)
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Learning Swift Second Edition

Learning Swift Second Edition

5 (1)
By: Andrew J Wagner
Buy this Book

Overview of this book

Swift is Apple’s new programming language and the future of iOS and OS X app development. It is a high-performance language that feels like a modern scripting language. On the surface, Swift is easy to jump into, but it has complex underpinnings that are critical to becoming proficient at turning an idea into reality. This book is an approachable, step-by-step introduction into programming with Swift for everyone. It begins by giving you an overview of the key features through practical examples and progresses to more advanced topics that help differentiate the proficient developers from the mediocre ones. It covers important concepts such as Variables, Optionals, Closures, Generics, and Memory Management. Mixed in with those concepts, it also helps you learn the art of programming such as maintainability, useful design patterns, and resources to further your knowledge. This all culminates in writing a basic iOS app that will get you well on your way to turning your own app ideas into reality.
Table of Contents (14 chapters)
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Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
1. Introducing Swift
1. Introducing Swift
Defining our goals for this book
Setting up the development environment
Running our first swift code
Understanding playgrounds
Learning with this book
Summary
2
2. Building Blocks – Variables, Collections, and Flow Control
2. Building Blocks – Variables, Collections, and Flow Control
Core Swift types
Swift's type system
Printing to the console
Control flow
Functions
Bringing it all together
Summary
3
3. One Piece at a Time – Types, Scopes, and Projects
3. One Piece at a Time – Types, Scopes, and Projects
Structs
Classes
Enumerations
Projects
Extensions
Scope
Access control
Summary
4
4. To Be or Not To Be – Optionals
4. To Be or Not To Be – Optionals
Defining an optional
Unwrapping an optional
Optional chaining
Implicitly unwrapped optionals
Debugging optionals
The underlying implementation
Summary
5
5. A Modern Paradigm – Closures and Functional Programming
5. A Modern Paradigm – Closures and Functional Programming
Functional programming philosophy
Closures
Building blocks of functional programming in Swift
Lazy evaluation
Example
Summary
6
6. Make Swift Work For You – Protocols and Generics
6. Make Swift Work For You – Protocols and Generics
Protocols
Generics
Extending generics
Putting protocols and generics to use
Summary
7
7. Everything Is Connected – Memory Management
7. Everything Is Connected – Memory Management
Computer data storage
Value types versus reference types
Automatic reference counting
Strong reference cycles
Lost objects
Structures versus classes
Summary
8
8. Paths Less Traveled – Error Handling
8. Paths Less Traveled – Error Handling
Throwing errors
Handling errors
Cleaning up in error situations
Summary
9
9. Writing Code the Swift Way – Design Patterns and Techniques
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9. Writing Code the Swift Way – Design Patterns and Techniques
What is a design pattern?
Behavioral patterns
Structural patterns
Creational patterns
Using associated values effectively
Extending system types to reduce code
Lazy properties
Summary
10
10. Harnessing the Past – Understanding and Translating Objective-C
10. Harnessing the Past – Understanding and Translating Objective-C
Swift's relationship to Objective-C
Background of Objective-C
Constants and variables
Containers
Control flow
Functions
Types
Projects
Calling Objective-C code from Swift
Using functions
Summary
11
11. A Whole New World – Developing an App
11. A Whole New World – Developing an App
Conceptualizing the app
Setting up the app project
Configuring the user interface
Running the app
Allowing picture taking
Temporarily saving a photo
Populating our photo grid
Refactoring to respect model-view-controller
Permanently saving a photo
Summary
12
12. What's Next? – Resources, Advice, and the Next Steps
12. What's Next? – Resources, Advice, and the Next Steps
Apple's documentation
Forums and blogs
Prominent figures
Podcasts
Summary
13
Index
Index

Lazy properties

One feature we have not yet discussed is the concept of lazy properties. Marking a property as lazy allows Swift to wait to initialize it until the first time it is accessed. This can be useful in at least a few important ways.

Avoiding unnecessary memory usage

The most obvious way to use lazy properties is to avoid unnecessary memory usage. Let's look at a very simple example first:

struct MyType {
    lazy var largeString = "Some String"
}
let instance = MyType()

Even though we created a new instance of MyType in the preceding code, largeString is not set until we try to access it. This is great if we have a large variable that may not be needed on every instance. Until it is accessed, it is not taking up any memory.

Avoiding unnecessary processing

We can also take this idea of a lazy property even further using a closure to calculate the value:

class Directory {
    lazy var subFolders: [Directory] = {
        var loaded = [Directory]()
        // Load subfolders into 'loaded...

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