Book Image

Learning Swift Second Edition - Second Edition

By : Andrew J Wagner
Book Image

Learning Swift Second Edition - Second Edition

By: Andrew J Wagner

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.

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Table of Contents (19 chapters)
Learning Swift Second Edition
Learning Swift Second Edition
Credits
Credits
About the Author
About the Author
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Introducing Swift
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
Building Blocks – Variables, Collections, and Flow Control
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
One Piece at a Time – Types, Scopes, and Projects
One Piece at a Time – Types, Scopes, and Projects
Structs
Classes
Enumerations
Projects
Extensions
Scope
Access control
Summary
4
To Be or Not To Be – Optionals
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
A Modern Paradigm – Closures and Functional Programming
A Modern Paradigm – Closures and Functional Programming
Functional programming philosophy
Closures
Building blocks of functional programming in Swift
Lazy evaluation
Example
Summary
6
Make Swift Work For You – Protocols and Generics
Make Swift Work For You – Protocols and Generics
Protocols
Generics
Extending generics
Putting protocols and generics to use
Summary
7
Everything Is Connected – Memory Management
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
Paths Less Traveled – Error Handling
Paths Less Traveled – Error Handling
Throwing errors
Handling errors
Cleaning up in error situations
Summary
9
Writing Code the Swift Way – Design Patterns and Techniques
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
Harnessing the Past – Understanding and Translating Objective-C
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
A Whole New World – Developing an App
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
What's Next? – Resources, Advice, and the Next Steps
What's Next? – Resources, Advice, and the Next Steps
Apple's documentation
Forums and blogs
Prominent figures
Podcasts
Summary
Index
Index

Closures

In Swift, functions are considered first-class citizens, which means that they can be treated the same as any other type. They can be assigned to variables and be passed in and out of other functions. When treated this way, we call them closures. This is an extremely critical piece to write more declarative code because it allows us to treat functionalities like objects. Instead of thinking of functions as a collection of code to be executed, we can start to think about them more like a recipe to get something done. Just like you can give just about any recipe to a chef to cook, you can create types and methods that take a closure to perform some customizable behavior.

Closures as variables

Let's take a look at how closures work in Swift. The simplest way to capture a closure in a variable is to define the function and then use its name to assign it to a variable:

func double(input: Int) -> Int {
        return input * 2
}

var doubleClosure = double
print(doubleClosure(2)) // 4...
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