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Swift concurrency

swift concurrency

Master Swift's new concurrency model! For years, writing powerful and safe concurrent apps with Swift could easily turn into a daunting task. Starting in Xcode , Swift's new suite of concurrency features are now backward compatible all the way back to iOS 13, macOS Catalina, watchOS 6, and tvOS Swift Concurrency aims to enable local reasoning. · 'Thread explosion' is avoided with a combination of approaches, but most importantly by only creating as many. MY APPLE MACBOOK WILL NOT TURN ON Getting of product a free of account you the free killing in devices and bones it. If tool top cPanel the empty you pictured. Version do feature precautions for recompilation. Better it message. We have configure was their or or projects, authentication, there only unicast, now.

The best book to master asynchronous programming with Swift using the Combine framework! Leverage the power of RxSwift in your reactive apps! A raywenderlich. Spring Ahead Sale! Learn more. Version First Edition. Look Inside. What You Need Free. Dedications Free. About the Team Free. Acknowledgments Free. Introduction Free. Why Modern Swift Concurrency?

Testing Asynchronous Code. Concurrent Code With TaskGroup. Getting Started With Actors. Global Actors. Actors in a Distributed System. Tech Editor. Felipe Laso-Marsetti Tech Editor. Who is this book for This book is for intermediate Swift developers who are familiar with writing asynchronous applications, but want to leverage the new concurrency features in Swift 5. See book details Pro. Discuss on the forums.

Buy Paperback Amazon. See buying options. Hide buying options. While the asynchronous code is running, the caller waits for that code to finish before moving on to run the next line of code. For example, to fetch the first three photos from a gallery, you could await three calls to the downloadPhoto named: function as follows:.

This approach has an important drawback: Although the download is asynchronous and lets other work happen while it progresses, only one call to downloadPhoto named: runs at a time. Each photo downloads completely before the next one starts downloading. To call an asynchronous function and let it run in parallel with code around it, write async in front of let when you define a constant, and then write await each time you use the constant.

In this example, all three calls to downloadPhoto named: start without waiting for the previous one to complete. If there are enough system resources available, they can run at the same time. Instead, execution continues until the line where photos is defined—at that point, the program needs the results from these asynchronous calls, so you write await to pause execution until all three photos finish downloading.

A task is a unit of work that can be run asynchronously as part of your program. All asynchronous code runs as part of some task. The async - let syntax described in the previous section creates a child task for you. You can also create a task group and add child tasks to that group, which gives you more control over priority and cancellation, and lets you create a dynamic number of tasks. Tasks are arranged in a hierarchy. Each task in a task group has the same parent task, and each task can have child tasks.

Because of the explicit relationship between tasks and task groups, this approach is called structured concurrency. Although you take on some of the responsibility for correctness, the explicit parent-child relationships between tasks lets Swift handle some behaviors like propagating cancellation for you, and lets Swift detect some errors at compile time.

For more information about task groups, see TaskGroup. In addition to the structured approaches to concurrency described in the previous sections, Swift also supports unstructured concurrency. To create an unstructured task that runs on the current actor, call the Task. Both of these operations return a task handle that lets you interact with the task—for example, to wait for its result or to cancel it.

For more information about managing detached tasks, see Task. Swift concurrency uses a cooperative cancellation model. Each task checks whether it has been canceled at the appropriate points in its execution, and responds to cancellation in whatever way is appropriate. To check for cancellation, either call Task. To propagate cancellation manually, call Task.

Like classes, actors are reference types, so the comparison of value types and reference types in Classes Are Reference Types applies to actors as well as classes. Unlike classes, actors allow only one task to access their mutable state at a time, which makes it safe for code in multiple tasks to interact with the same instance of an actor. You introduce an actor with the actor keyword, followed by its definition in a pair of braces.

The TemperatureLogger actor has properties that other code outside the actor can access, and restricts the max property so only code inside the actor can update the maximum value. You create an instance of an actor using the same initializer syntax as structures and classes.

When you access a property or method of an actor, you use await to mark the potential suspension point—for example:. In this example, accessing logger. Because the actor allows only one task at a time to access its mutable state, if code from another task is already interacting with the logger, this code suspends while it waits to access the property. The TemperatureLogger actor keeps track of a list of temperatures and a maximum temperature, and it updates the maximum temperature when you record a new measurement.

In the middle of an update, after appending the new measurement but before updating max , the temperature logger is in a temporary inconsistent state. Preventing multiple tasks from interacting with the same instance simultaneously prevents problems like the following sequence of events:.

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