Скачать или смотреть How to Change @ EnvironmentObject in SwiftUI from a Class Instead of a View

Learn how to effectively manipulate `@ EnvironmentObject` in SwiftUI even from a class that is not a View. This guide offers insights and solutions for common issues faced in SwiftUI development.
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This video is based on the question https://stackoverflow.com/q/62780775/ asked by the user 'Alina' ( https://stackoverflow.com/u/6150703/ ) and on the answer https://stackoverflow.com/a/62780948/ 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 @ EnvironmentObject in SwiftUI

SwiftUI provides a powerful way to manage state across your application. One useful property wrapper is @ EnvironmentObject, which allows you to share data between views seamlessly. However, developers sometimes run into challenges, especially when trying to update @ EnvironmentObject from a class rather than a View.

In this guide, we'll explore a common scenario where you might encounter an error and how to effectively resolve it by modifying @ EnvironmentObject from within a class.

The Problem: Accessing @ EnvironmentObject from a Class

Imagine you have a SwiftUI application with a TabView that contains two child views: PageOneView and PageTwoView. Each of these views has its own nested child views. For instance, while PageTwoView has a nested child that can successfully access and modify the @ EnvironmentObject, PageOneView tries to do the same with a class, resulting in the following error:

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This occurs because @ EnvironmentObject is only applicable to Views and cannot directly be used in classes. So, how can we bypass this limitation and successfully update @ EnvironmentObject from a class?

The Solution: Pass the Instance Directly

To modify the @ EnvironmentObject from a class, you'll need to take a different approach. You don't use the @ EnvironmentObject property wrapper within your class; instead, you pass the instance of your data directly. Here’s how you can implement this solution.

Modify Your Class

Instead of trying to access @ EnvironmentObject in your Child class, you define a constructor that accepts an instance of Data. This allows you to update the shared data without needing the view-specific wrapper.

Here’s how to adjust your existing code:

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

The Key Changes

Remove @ EnvironmentObject in the Class: The Child class no longer uses the @ EnvironmentObject property wrapper.

Pass Data as a Constructor Argument: The Child class receives an instance of Data through its initializer, allowing it to manipulate the data without needing it to be an EnvironmentObject.

Conclusion

By passing the instance of Data directly to your class, you can efficiently manage and update your application's state without running into the limitations of @ EnvironmentObject. This approach maintains clarity and adheres to SwiftUI data management principles while providing flexibility in how instances and updates are handled.

Next time you find yourself struggling to update @ EnvironmentObject from classes, remember to pass the data instance directly and avoid using the @ EnvironmentObject wrapper in situations where it is not suitable.

Happy coding in SwiftUI!