Скачать или смотреть How to Create a struct Parameter That is a Closure Returning some View in SwiftUI

Learn how to create generic reusable views in SwiftUI that return specific views without the need for `AnyView` wrappers.
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This video is based on the question https://stackoverflow.com/q/65810765/ asked by the user 'Marco Boerner' ( https://stackoverflow.com/u/12764795/ ) and on the answer https://stackoverflow.com/a/65811046/ provided by the user 'Dávid Pásztor' ( https://stackoverflow.com/u/4667835/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Create a struct Parameter That is a Closure Returning some View in SwiftUI

When building applications with SwiftUI, creating reusable components is essential. However, you might encounter challenges when trying to structure your views to be flexible enough to accept various input types. A common struggle is finding a way to have a closure as a parameter that returns a specific view type, allowing for greater usability without relying on AnyView. This guide will address that issue and provide a clear, organized solution.

Current Situation

Imagine you are working on a SwiftUI project where you need to create a reusable view. Currently, you are using a closure that returns AnyView, which forces you to wrap custom views like CustomViewA or CustomViewB inside AnyView(). This approach is not optimal as it sacrifices type safety and introduces unnecessary complexity.

The Challenge

You want a way to pass custom views directly into your reusable view without wrapping them in AnyView. However, when you tried changing the closure parameter to return some View, Swift gives you the following error:

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This error indicates that you can't use some View directly in your closure type in this context, leaving you searching for alternatives.

The Solution

To achieve your goal, you can make your ReusableView generic. By doing this, you will declare a generic type for the closure's return value rather than relying on AnyView. Let’s explore how you can implement this solution effectively.

Step-by-Step Breakdown

Make the ReusableView Generic:
You need to declare your ReusableView struct as generic, parameterized by Output: View. This change allows your view to accept any type that conforms to the View protocol.

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Define Your Custom Views:
Let's assume you have two custom views that you want to use: CustomViewA and CustomViewB. Here's how they might look (no changes are needed here if you have defined them already).

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Usage in the Preview Provider:
Finally, in your ContentView_Previews, you can instantiate ReusableView, passing in your custom view directly without any wrappers.

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Conclusion

By making the ReusableView generic and typing the closure parameter to return a specific view type, you successfully eliminate the need for AnyView. This not only simplifies your code, but it also retains type safety, leading to fewer potential runtime errors. Now you can seamlessly pass different views to your reusable component as needed.

Feel free to try this approach in your SwiftUI projects, and enjoy the flexibility it brings to your UI development process!