Book Image

Mastering Swift 5 - Fifth Edition

By : Jon Hoffman
Book Image

Mastering Swift 5 - Fifth Edition

By: Jon Hoffman

Overview of this book

Over the years, the Mastering Swift book has established itself amongst developers as a popular choice as an in-depth and practical guide to the Swift programming language. The latest edition is fully updated and revised to cover the new version: Swift 5. Inside this book, you'll find the key features of Swift 5 easily explained with complete sets of examples. From the basics of the language to popular features such as concurrency, generics, and memory management, this definitive guide will help you develop your expertise and mastery of the Swift language. Mastering Swift 5, Fifth Edition will give you an in-depth knowledge of some of the most sophisticated elements in Swift development, including protocol extensions, error handling, and closures. It will guide you on how to use and apply them in your own projects. Later, you'll see how to leverage the power of protocol-oriented programming to write flexible and easier-to-manage code. You will also see how to add the copy-on-write feature to your custom value types and how to avoid memory management issues caused by strong reference cycles.
Table of Contents (20 chapters)

The need for optional types in Swift

Now, the burning question: 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 two, 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...