Скачать или смотреть Resolving EXC_BAD_ACCESS: Avoid Async @objc Selector Crashes in Swift 5.5

Explore how to prevent the `EXC_BAD_ACCESS` error when using async functions as @objc selectors in Swift 5.5. Discover effective strategies for implementing refresh control smoothly.
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Resolving EXC_BAD_ACCESS: Avoid Async @objc Selector Crashes in Swift 5.5

When developing applications with Swift 5.5, developers might encounter unexpected crashes while dealing with async functions in a refresh control. A common issue arises when @objc selectors are used alongside async methods, leading to a frustrating EXC_BAD_ACCESS error. This guide focuses on understanding this problem and providing a clear solution to avoid crashes in your iOS applications.

Understanding the Problem

In many cases, developers implement UIRefreshControl to allow users to refresh content in a UITableView. In the example at hand, after resetting the data source and making an asynchronous API call to fetch new data, the app crashes with an error that reads:

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Why Does This Happen?

The underlying reason for this error is that @objc methods cannot be marked as async. When such a method is called as a selector (for example, when the user pulls to refresh), it leads to a runtime crash due to improper threading and execution contexts.

Solution: Using Wrapper Selectors for Async Methods

To prevent this crash, the key is to create a wrapper for your async methods. Here’s how you can do it effectively.

Step 1: Define the Wrapper Selector

Instead of marking your didPullToRefresh method as async, you should create a separate, synchronous method that serves as the selector. This method will handle the task of calling the async function.

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Step 2: Update the Async Method

We’ll keep the original async method for executing the network call, but it will no longer directly serve as a selector.

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Step 3: Modify Your Refresh Control Setup

Finally, you need to ensure that your UIRefreshControl is correctly set up to use the new wrapper selector.

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Optional: Handing Refresh Control State

Don’t forget to handle the refresh control’s state (like ending refreshing) after your data is fetched to improve user experience. For example:

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Conclusion

By implementing a wrapper for your async methods, you can effectively avoid the EXC_BAD_ACCESS error caused by using async @objc selectors in Swift 5.5. This approach not only enhances the stability of your application but also maintains the clarity and organization of your code.

With these strategies, you can continue to utilize the power of async/await while ensuring that your app's user experience remains seamless and crash-free. Happy coding!