Скачать или смотреть Resolving SwiftUI View Update Issues with @ Binding and @ EnvironmentObject

Discover how to fix SwiftUI view update issues with a step-by-step guide on using `@ Binding` and `@ EnvironmentObject` effectively.
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This video is based on the question https://stackoverflow.com/q/71723343/ asked by the user 'BONIX SULOD' ( https://stackoverflow.com/u/5275487/ ) and on the answer https://stackoverflow.com/a/71723609/ provided by the user 'HunterLion' ( https://stackoverflow.com/u/18251327/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting SwiftUI View Updates: Understanding @ Binding and @ EnvironmentObject

If you are new to SwiftUI, you might encounter a situation where your views don't update as expected when you modify a bound property. This can be quite confusing and frustrating. For instance, a common issue arises when developers try to use a @ Binding property to manage the state of a view element, yet the view does not reflect these changes. Let’s take a closer look at a specific case involving a favorite button that toggles a landmark's favorite state.

The Problem: Views Not Updating

Consider the following scenario where you have a Toggle button that is intended to change whether a landmark is marked as a favorite. The relevant code involves a FavoriteButton that binds its state to an isFavorite property in the ModelData environment object. However, when the button is activated, the underlying view does not update, even though the data seems to change in the console logs.

Key Snippet

Here's a sketch of the structure you are dealing with:

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

Despite toggling the isSet property, the rest of the view hierarchy does not reflect these changes.

Understanding the Solution

To resolve this issue, we need to reconsider how and where we are managing and reading the state of our data. Below, we break the solution down into clear sections.

Step 1: Use @ EnvironmentObject Instead of @ Binding

In your scenario, the FavoriteButton should directly access the environment object rather than relying on the @ Binding property. By utilizing the environment object, you can modify the model directly without dealing with bindings.

Step 2: Modifying the FavoriteButton

Here’s how you can redefine your FavoriteButton to read from the ModelData and toggle the state appropriately:

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

Step 3: Passing the Index

In the parent view, you need to pass the index of the landmark that your FavoriteButton will modify:

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

Key Points to Remember

Read from Environment: Use @ EnvironmentObject to access the shared state.

Toggle Directly: Modify the model directly from the button action instead of through a binding.

ObservableObject: Ensure that your ModelData class conforms to ObservableObject and is correctly set in the environment.

Wrapping Up

By implementing these changes, you will enable your FavoriteButton to effectively toggle the favorite state of landmarks and ensure your views update correctly in response to changes. Always remember to utilize @ EnvironmentObject when you are already working with a shared environment model, as it can simplify your state management in SwiftUI.

With practice and an understanding of these concepts, you'll find that managing state in SwiftUI becomes much clearer and more manageable!