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Discover how to resolve the "Attempt to create two animations for cell" error when reordering sections in SwiftUI's List from a separate view.
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How to Reorder Dynamic Sections in SwiftUI Using Another View

One common challenge faced by SwiftUI developers is dynamically reordering sections within a list from a different view. When working with an ObservableObject, changes made in subviews sometimes do not propagate as expected, leading to frustrating issues such as "Attempt to create two animations for cell" error. In this post, we will explore a solution for this problem by simplifying data management between views and ensuring smooth interactions with the UI.

The Problem

Imagine you have a simple list organized into sections, managed by an ObservableObject. You want to allow users to reorder these sections from a separate view. When attempting to do this, you may encounter issues due to SwiftUI's state handling, particularly when changes aren't properly reflected across views. This behavior can lead to unexpected errors during the reordering process.

To better illustrate, consider the following basic code setup:

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

Here, the ViewModel holds an array of sections. We can move sections using the move function. However, issues arise when these modifications are attempted from another view, like this one:

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

The Solution

To effectively solve the problem, we will decouple the binding from our views. Instead of directly manipulating the sections from the OrderingView, we will explicitly pass the sections down and use a callback to return changes back to the parent view. This way, alterations are clearer, and we reduce the complexity of state management.

Step 1: Modify ContentView

We need to adjust the way we are presenting OrderingView in ContentView. Here’s how we can implement this change:

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

In this code, we pass the sections to OrderingView along with a closure (callback) that updates the sections when reordering is done.

Step 2: Adjust OrderingView

Now, we will need to enhance OrderingView to accept the sections and callback. Here’s how the new structure looks:

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

Explanation of Changes

Data Passing: Instead of relying on @ ObservedObject, we use an array passed directly to OrderingView, making changes local and independent.

Callback: This allows us to return the potentially modified sections back to ContentView, updating the view model’s state in the parent view as needed.

By implementing these modifications, the section reordering functionality works seamlessly, and you avoid the animation errors caused by SwiftUI state management quirks.

Conclusion

Reordering sections in a SwiftUI list can be challenging, especially when modifying values spread across multiple views. By passing data explicitly and using callbacks for updates, we can enhance our app's structure and maintain a clean state without running into common pitfalls. Ensure to test these changes with your own data and setup, and enjoy a smooth user experience on your SwiftUI apps!