Book Image

Mastering Swift 3

Book Image

Mastering Swift 3

Overview of this book

Swift is the definitive language of Apple development today. It’s a vital part of any iOS and OS X developer’s skillset, helping them to build the most impressive and popular apps on the App Store—the sort of apps that are essential to iPhone and iPad users every day. With version 3.0, the Swift team have added new features to improve the development experience—making it easier to get the results you want and customers expect. Inside, you’ll find the key features of Swift 3.0 and quickly learn how to use the newest updates to your development advantage. From Objective-C interoperability to ARC, to closures and concurrency, this advanced Swift guide will develop your expertise and make you more fluent in this vital programming language. We give you in-depth knowledge of some of the most sophisticated elements of Swift development including protocol extensions, error-handling, design patterns, and concurrency, and guide you on how to use and apply them in your own projects. You'll see how even the most challenging design patterns and programming techniques can be used to write cleaner code and to build more performant iOS and OS X applications. By the end of this book, you’ll have a handle on effective design patterns and techniques, which means you’ll soon be writing better iOS and OS X applications with a new level of sophistication and control.
Table of Contents (23 chapters)
Mastering Swift 3
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Free Chapter
1
Taking the First Steps with Swift
2
Learning About Variables, Constants, Strings, and Operators

The need for optional types in Swift


Now, the burning question is why does Swift need optionals? To understand this question, we should examine what problems optionals are designed to solve.

In most languages, it is possible to create a variable without giving it an initialized value. For example, in Objective-C, both of these lines of code are valid:

int i; 
MyObject *m; 

Now, let's say that the MyObject class, written in Objective-C, has the following method:

-(int)myMethodWithValue:(int)i { 
    return i*2; 
} 

This method takes the value passed in from the i parameter, multiplies it by 2, and returns the results. Let's try to call this method using the following code:

MyObject *m; 
NSLog(@"Value: %d",[m myMethodWithValue:5]); 

Our first thought might be that this code would display Value: 10 since we are passing the value of 5 to a method that doubles the value passed in; however, this would be incorrect. In reality, this code would display Value: 0 because...