Скачать или смотреть Return Some View in SwiftUI: Handling Multiple States with Ease

Discover how to return generic View types in SwiftUI when managing multiple app states effectively. Learn about `@ ViewBuilder` and structuring your SwiftUI views optimally.
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This video is based on the question https://stackoverflow.com/q/62715374/ asked by the user 'user499846' ( https://stackoverflow.com/u/499846/ ) and on the answer https://stackoverflow.com/a/62715713/ 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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Navigating SwiftUI: How to Return a Generic View Type

If you're making the jump into SwiftUI and have hit a roadblock, you're not alone. As you build your app's home screen, you may find yourself needing a way to navigate different visual states based on certain conditions. This can challenge your understanding of SwiftUI as it diverges from how you might handle similar tasks in UIKit or other frameworks. Let’s tackle this common problem and explore a clean solution.

The Challenge

You want to create a struct that evaluates some state data and returns the appropriate View accordingly. In UIKit, you might leverage a Manager object and return a UIView class. However, trying to implement the same logic in SwiftUI can lead to errors and confusion.

For example, you might start with code like this:

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This approach generates an error: "Protocol 'View' can only be used as a generic constraint because it has Self or associated type requirements." Essentially, SwiftUI's View protocol has strict rules regarding its return types that can trip up developers accustomed to UIKit.

The Solution: Using @ ViewBuilder with some View

Instead of returning View, you can harness the power of @ ViewBuilder in conjunction with some View. This allows you to create a method that can return multiple views based on conditions without the limitations you've encountered. Here’s how to do it:

1. Update Your Struct and Method Signature

Replace the existing fetchView() method with the following:

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

2. Understand the Components

@ ViewBuilder: This attribute allows your method to return multiple views. It acts as a builder that can compose a series of Views into a single output.

some View: This tells SwiftUI that your method will return a specific type of View, without needing to specify the exact type at the point of declaration.

3. Implement Your Views

Here are the two View structs being referenced:

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

Conclusion

Utilizing @ ViewBuilder combined with some View provides a powerful way to manage the differing visual states in your SwiftUI applications. This approach not only addresses the protocol constraints but also maintains clarity and elegance in your code. By adapting your thinking from UIKit-centric practices to embrace SwiftUI’s components, you'll unlock the full potential of this modern framework.

Happy coding, and may your SwiftUI journey be smooth and rewarding!