Announcing New Course: iOS Concurrency with GCD & Operations!

Introducing Our New Course: iOS Concurrency with GCD & Operations!

Dispatch queues? Operations? Race conditions? Priority inversion? Deadlock? That all may sound intimidating, but these things are crucial to providing your users with a fluid and responsive experience in your app — and fortunately, they're easier to understand than you think.

Learn how to give your users a great, responsive experience, manage groups of tasks with dependencies and leverage asynchronous API methods in dispatch groups and operation queues with our new iOS Concurrency with GCD & Operations course!

Keep reading to hear more about it from course instructor Audrey Tam:

Why should I take your iOS Concurrency with GCD & Operations course?

"Every iOS developer needs to learn how to add concurrency to apps, moving slow tasks off the main queue to keep the user interface responsive.

But doing this can cause seemingly random problems that are hard to debug, like data races, priority inversion and deadlock. My course teaches you how these problems arise and how you can avoid them."

How can this course help with a common pain point in iOS development?

"This course covers both Grand Central Dispatch and OperationQueues, the two APIs that help you make synchronous tasks asynchronous. That is, they take tasks that would block the main queue and move them to another queue, so the main queue can carry on with responding to the user.

Now there are APIs that are asynchronous by nature, like URLSession. All you have to do is remember to perform any consequent UI updates on the main queue. But a surprising amount of this course is about wrapping these asynchronous functions so they look synchronous. This is because dispatch groups and operation queues need to know when they really finish, in order to manage a sequence of tasks."

Can you please share a cool concurrency tip with us?

"Apple solves the problem of priority inversion by promoting lower priority tasks in a queue to the same level as the high priority task. This can actually cause priority inversion if you dispatch a task from the main queue onto a private utility queue, because that task's default quality of service is user-initiated. So the utility queue gets promoted to user-initiated!

The solution is to create a dispatch work item in a task running on the utility queue and use its assignCurrentContext flag to capture the utility quality of service level. Then you can dispatch it from anywhere, including the main queue, to a utility queue, and it won't promote that queue's priority."

Is there anything else we should know about your iOS Concurrency with GCD & Operations course?

"It's easy to get confused about serial vs. concurrent queues and synchronous vs. asynchronous dispatch. I explain these concepts very early in the course. Basically, synchronous vs. asynchronous is about the source of the task and serial vs. concurrent is about the destination of the task. If that sounds kind of cryptic, come and watch my course! ;]"

Audrey's iOS Concurrency with GCD & Operations course is available for subscribers now!

— Ray