How to Convert GCD Code to async/await in Swift

Discover the best practices for converting your GCD-based async code to `async/await` in Swift, and learn how to handle completion in an effective way.
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Converting GCD Code to async/await in Swift

In the world of Swift programming, asynchronous tasks often involve completion handlers to manage code execution. However, with the introduction of async/await, developers now have a cleaner and more efficient way to handle asynchronous operations. In this post, we'll explore how to convert a traditional GCD (Grand Central Dispatch) pattern into async/await, particularly focusing on the implementation of a performTask function.

Understanding the Problem

Let's start with a typical code structure using GCD:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Current Implementation

Function Explanation:

performTask accepts a completion handler.

It calls doSomeAsyncTask, which performs an asynchronous task and returns a success status.

Based on isSuccess, it either handles the result or calls the completion closure.

Challenge:

The existing setup uses completion handlers which can become cumbersome, especially when nesting multiple asynchronous calls.

Transitioning to async/await

Here's how to rewrite the performTask function with async/await:

Basic Structure

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the New Implementation

@ discardableResult: This attribute indicates that the caller of the function can ignore the return value if they choose to do so. This is a useful practice, especially when the success or failure of the task might not always require immediate attention.

isSuccess: This variable stores the result of the asynchronous task, obtained via await doSomeAsyncTask(). The function will wait for this task to complete before proceeding.

Conditional Logic:

If isSuccess is true, the function directly awaits handleResult().

If isSuccess is false, handleResult() is triggered asynchronously within a new Task, allowing the performTask method to finish returning quicker.

Alternative Error Handling

Sometimes, rather than returning a boolean, it might be beneficial to throw an error when the task fails. Here’s how you could implement that:

[[See Video to Reveal this Text or Code Snippet]]

Simpler Approach

For simplicity in certain contexts, the following approach might be more efficient:

[[See Video to Reveal this Text or Code Snippet]]

By directly awaiting handleResult(), we streamline the flow and eliminate unnecessary complexity unless you specifically need the asynchronous behavior during a failure.

Conclusion

Transitioning from GCD to async/await not only simplifies your code but also enhances readability and maintainability. Understanding how to handle different outcomes is critical in ensuring that your Swift functions behave as expected. Whether utilizing completion handlers or adopting the async/await model, selecting the right approach will lead to more efficient and effective code.

By keeping these strategies in mind, you'll be well on your way to mastering asynchronous programming in Swift!