Скачать или смотреть Resolving the Error when running a FetchRequest in Core Data with SwiftUI

Encountering an `EXC_BREAKPOINT` error with FetchRequest in SwiftUI? Learn how to properly implement a Core Data fetch request in your SwiftUI applications.
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This video is based on the question https://stackoverflow.com/q/63030450/ asked by the user 'Michel' ( https://stackoverflow.com/u/611201/ ) and on the answer https://stackoverflow.com/a/63030851/ provided by the user 'Asperi' ( https://stackoverflow.com/u/12299030/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the FetchRequest Error in SwiftUI

When developing apps using SwiftUI and Core Data, many developers encounter issues that can lead to frustrating errors. One such error is the EXC_BREAKPOINT, which can occur while trying to utilize FetchRequest. In this post, we'll break down the problem in detail and provide you with a clear and effective solution.

The Problem: FetchRequest Misuse

In the provided code snippet, the developer attempts to execute a FetchRequest within a method. The error arises from incorrect usage. The FetchRequest is a property wrapper designed to work in a SwiftUI view, not within a regular function. Here’s a look at the problematic code:

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When trying to run this line, the app crashes with the following error:

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This suggests an issue with how the FetchRequest is being instantiated and utilized, given that it is not designed for use outside of a SwiftUI view's context.

The Solution: Proper Use of NSFetchRequest

Instead of using FetchRequest directly in the function body, leverage NSFetchRequest to retrieve the data you need. This approach is not only valid but also aligns with the intended use of Core Data in Swift. Here’s how you can refactor your code:

Step 1: Create an NSFetchRequest

Define an NSFetchRequest to fetch your MyEntity objects based on a specific predicate:

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Step 2: Perform the Fetch

Instead of trying to use FetchRequest as a property wrapper, use try? to fetch the count directly from your context:

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Conclusion

By switching from FetchRequest to NSFetchRequest, you can avoid the EXC_BREAKPOINT error and successfully retrieve your data without crashing the app. This change ensures that your code adheres to best practices while enabling you to perform data calculations effectively.

Next time you encounter issues with Core Data in your SwiftUI applications, remember this approach for using NSFetchRequest. Happy coding!