Cancellation handling in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is cancellation handling in Swift concurrency?

Cancellation handling is the process of stopping a running asynchronous task when it is no longer needed, allowing the program to free resources and avoid unnecessary work.

beginner

How do you check if a Swift Task has been cancelled?

You check if a task has been cancelled by using the property Task.isCancelled inside the task's code.

intermediate

What happens if you throw CancellationError in a Swift async task?

Throwing CancellationError signals that the task was cancelled and allows the task to exit early and clean up resources.

intermediate

Why should you check for cancellation regularly inside long-running async tasks?

Because it lets the task stop work early if cancellation is requested, saving CPU time and improving app responsiveness.

beginner

How do you cancel a running Swift Task?

You call the cancel() method on the Task instance you want to stop.

Which property tells you if a Swift Task has been cancelled?

A Task.isCancelled

B Task.isRunning

C Task.isComplete

D Task.isPaused

Task.isCancelled is true when a cancellation request has been made for the task.

What method do you call to request cancellation of a Swift Task?

A stop()

B cancel()

C terminate()

D end()

The cancel() method requests the task to stop as soon as possible.

What error type is commonly thrown to indicate a cancelled task in Swift concurrency?

A AsyncError

B TaskError

C CancellationError

D StopError

CancellationError is the standard error used to signal task cancellation.

Why is it important to check for cancellation inside a long-running async task?

A To log task progress

B To restart the task automatically

C To increase task priority

D To free resources and stop unnecessary work

Checking for cancellation lets the task stop early and save resources.

What happens if you ignore cancellation requests in a Swift Task?

A The task will continue running until completion

B The task will stop immediately

C The task will throw an error automatically

D The task will pause

Ignoring cancellation means the task keeps running and wastes resources.

Explain how to implement cancellation handling in a Swift async task.

Think about how to detect and respond to cancellation requests inside the task.

Why is cancellation handling important in asynchronous programming?

Consider what happens if tasks run without stopping when they should.