Learn what is Concurrency and why would you even want to utilize it in your apps? Learn about Grand Central Dispatch, Apple’s implementation of C’s libdispatch, also known as GCD, as it’s one of the simplest ways to queue up tasks to be run in parallel. Then, take on Operations & Operation Queues for when GCD doesn’t quite cut it; you’ll learn how to further customize and reuse your concurrent work. You’ll then learn common concurrency problems that you could face while developing concurrent applications, such as Race Conditions, Deadlocks, and more. Finally, understand threads and thread sanitizer and the various threading-related concepts and how these connect to the knowledge you’ve accumulated throughout this book. You’ll also learn how to use Thread Sanitizer to ease your debugging when things go wrong.
Before You Begin
This section tells you a few things you need to know before you get started, such as what you’ll need for hardware and software, where to find the project files for this book, and more.
Concurrency can be handled by either Grand Central Dispatch (GCD) or Operations. Learn about the differences.
Section II: Grand Central Dispatch
In this section, you’ll take a deep dive into Apple’s most popular and easy-to-use mechanism to write and manage concurrent tasks — Grand Central Dispatch. You’ll learn how to utilize queues and threads to control the execution of tasks in your app, as well as how to group these tasks together. You’ll also learn about common pitfalls and dangers of using concurrency, and how you can avoid them.
In the previous chapter you learned about how queues work. In this chapter you'll expand that knowledge to learn how to submit multiple tasks to a queue which need to run together as a "group" so that you can be notified when they have all completed. You'll also learn how to wrap an existing API so that you can call it asynchronously.
By now you know how GCD can make your app so much faster. This chapter will show you some of the dangers of concurrency if you're not careful, and how to avoid them.
Section III: Operations
Even though Grand Central Dispatch provides most of the concurrency capabilties you’ll need right out-of-the-box, sometimes you’ll want some extra customizability. This is where Operations come into play. This section will teach you about Operations, Operation Queues, and everything in between.
Now that you can create an Operation and submit it to a queue, you'll learn how to make the operation itself asynchronous. While not something you'll do regularly, it's important to know that it's possible.
There are times when you need to stop an operation that is running, or has yet to start. This chapter will teach you the concepts that you need to be aware of to support cancelation.
Section IV: Real-Life Concurrency
To wrap up this book, this section will be dedicated to showing you how all of the knowledge you’ve accumulated throughout this book could be used for some real-life purposes.
In this section, you’ll take a deeper dive into a common case where concurrency plays a huge role — Core Data — as well as learn about Apple’s Thread Sanitizer as a great tool to debug and resolve concurrency issues and confusions.
Data races occur when multiple threads access the same memory without synchronization and at least one access is a write. This chapter will teach you how to use Apple's Thread Sanitizer to detect data races.
Shai is the iOS Tech Lead @ Gett, the on-demand mobility company. On his spare time you can find him active on several...
Who is this book for
This book is for intermediate iOS developers who already know the basics of iOS and Swift
development but want to learn how to make their app efficiently perform tasks without
affecting performance, and how to properly divide work to utilize hardware to the fullest extent.