Скачать или смотреть How to Fix @State Variable Not Updating from @Published in SwiftUI

Discover the solution to the issue of `@State` variables not updating from `@Published` properties in SwiftUI, ensuring your alerts behave as expected.
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Fixing Your SwiftUI @State Variable Not Updating from @Published

If you're diving into the world of SwiftUI and Combine, you might have encountered the frustrating issue where your @State variable never seems to get updated from a @Published property. This could lead to scenarios where essential alerts or UI elements fail to respond to changes in your model. In this guide, we’ll explore a common example and provide a clear solution to ensure that your SwiftUI application works seamlessly.

The Problem: @State Variable Not Triggering Alerts

Consider a SwiftUI view where you want to show an alert based on a condition set in your view model. Here’s what the initial implementation might look like:

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

In the above code, the showAlert is initialized with the value from the view model. However, if viewModel.showAlert changes later, showAlert in ContentView won’t update to reflect that change. This issue arises because the assignment of showAlert occurs only once during initialization, and there's no mechanism to observe changes afterward.

The Solution: Use @StateObject Instead

To fix the issue, you should replace your @ObservedObject with @StateObject. This allows your view to observe changes directly from the viewModel without needing a separate @State variable for showAlert. Here's how to implement it:

Step-by-Step Solution

Modify the Declaration of viewModel: Change @ObservedObject to @StateObject for the view model. This allows the view to own the model and react to changes.

Remove the @State Variable: You don’t need a separate state variable for the alert. Instead, observe the published property directly.

Here’s the updated code:

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

Why This Works

By utilizing @StateObject, your ContentView can reactively respond to the changes in viewModel.showAlert. When showAlert changes in the ViewModel, it automatically updates in the view, ensuring the alert is presented when needed.

Summary

In summary, when dealing with SwiftUI and Combine, always ensure that you’re correctly managing your state. Using @StateObject for your view models ensures that your views maintain a strong connection to their underlying data, leading to a more responsive user interface.

With this fix, you can now ensure alerts appear as intended based on your model’s state, improving the overall user experience of your application.

By addressing this common issue, you’re stepping up your SwiftUI development game!