Скачать или смотреть Using @ EnvironmentObject Properties with CADisplayLink in SwiftUI

Discover how to effectively use `CADisplayLink` in conjunction with `@ EnvironmentObject` properties in SwiftUI while avoiding common pitfalls.
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This video is based on the question https://stackoverflow.com/q/64068946/ asked by the user 'West1' ( https://stackoverflow.com/u/3919052/ ) and on the answer https://stackoverflow.com/a/64069037/ 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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Using @ EnvironmentObject Properties with CADisplayLink in SwiftUI

When working with animations in SwiftUI, you might encounter challenges integrating CADisplayLink with environment objects. One common error developers face is the message: "No ObservableObject of type MainData found. A View.environmentObject(_:) for MainData may be missing as an ancestor of this view." This indicates an issue with accessing the environment object correctly. Let's delve into this issue and explore a solution.

The Problem: Environment Object Accessibility

Using CADisplayLink can significantly enhance the animation experience in your application. However, if you attempt to access properties of an @ EnvironmentObject within a class that isn’t a SwiftUI view, you'll run into issues. Consider the example code:

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

In the MyAnimations class, the attempt to use @ EnvironmentObject results in a runtime error when trying to manipulate properties like displayLinkX and displayLinkY. This occurs because @ EnvironmentObject is designed for use within SwiftUI views, and classes like MyAnimations don’t have access to the environment directly.

The Solution: Refactor to Pass Data

To resolve this issue, you will need to refactor the MyAnimations class. Instead of relying on @ EnvironmentObject, you’ll explicitly pass the MainData object into the MyAnimations instance. Here’s how to achieve that:

Step-by-Step Refactoring

Remove @ EnvironmentObject: Since @ EnvironmentObject is not accessible in your non-view class, you need to remove it from MyAnimations.

Add an Initializer: Modify the class to accept MainData as a parameter through its initializer.

Here’s the updated code:

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

Connecting the Dots

Now, when you create an instance of MyAnimations from your ContentView, you should pass the mainData object like so:

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

By doing this, you ensure that the mainData instance is properly scoped and accessible without relying on the environmental context that @ EnvironmentObject provides.

Conclusion

Using CADisplayLink in SwiftUI to manage animations doesn't have to be complicated. By understanding the limitations of @ EnvironmentObject within non-view classes, you can effectively adjust your implementation approach. This solution not only resolves the issue but also adheres to best practices by maintaining a clean architecture in your SwiftUI applications.

If you find yourself needing to access environment data in non-SwiftUI sections of your code, consider passing objects explicitly or using DI (Dependency Injection) principles to keep your code organized and error-free. Happy coding!