Book Image

Swift High Performance

By : Kostiantyn Koval
Book Image

Swift High Performance

By: Kostiantyn Koval

Overview of this book

Swift is one of the most popular and powerful programming languages for building iOS and Mac OS applications, and continues to evolve with new features and capabilities. Swift is considered a replacement to Objective-C and has performance advantages over Objective-C and Python. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Develop Swift and discover best practices that allow you to build solid applications and optimize their performance. First, a few of performance characteristics of Swift will be explained. You will implement new tools available in Swift, including Playgrounds and REPL. These will improve your code efficiency, enable you to analyse Swift code, and enhance performance. Next, the importance of building solid applications using multithreading concurrency and multi-core device architecture is covered, before moving on to best practices and techniques that you should utilize when building high performance applications, such as concurrency and lazy-loading. Finally, you will explore the underlying structure of Swift further, and learn how to disassemble and compile Swift code.
Table of Contents (15 chapters)
Swift High Performance
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Avoiding Objective-C


You have learned that Objective-C (with its dynamic runtime) in most cases performs more slowly than Swift. Interoperability between Swift and Objective-C is done so seamlessly that sometimes we can use Objective-C types and its runtime in the Swift code without knowing that.

When you use Objective-C types in Swift code, Swift is actually using the Objective-C runtime for method dispatch. Because of that, Swift can't do the same optimization as for pure Swift types. Let's have a look at a simple example:

  for _ in 0...100 {
    _ = NSObject()
  }

Let's read this code and make some assumptions about how the Swift compiler would optimize that code. The NSObject instance is never used in the loop body, so we could eliminate creating an object. After that we would have an empty loop that could also be eliminated. So we would remove all the code from execution.

Let's see what is happening in reality by looking at generated assembly pseudocode:

rbx = 0x65;
  do {
    rax = [_OBJC_CLASS_...