Скачать или смотреть How to Pass a View as Parameter to a Button Triggering a Modal in SwiftUI

Discover how to troubleshoot and correctly implement a custom button in SwiftUI that opens a modal with a view passed as a parameter.
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This video is based on the question https://stackoverflow.com/q/62329093/ asked by the user 'sonja' ( https://stackoverflow.com/u/8411754/ ) and on the answer https://stackoverflow.com/a/62330217/ 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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How to Pass a View as Parameter to a Button Triggering a Modal in SwiftUI

Creating custom buttons that can trigger modals can sometimes be tricky in SwiftUI. If you’re working with a custom button that takes a view as a parameter but finds that the view is always empty when the button is clicked, you are not alone. In this guide, we will explore this issue and provide a clear solution to make your button work as intended.

The Problem

In a recent project, a developer faced a frustrating problem: a custom button struct intended to show a modal view. Despite receiving the warning that the infoPage variable was always empty, they couldn't pinpoint the source of the error. The relevant code snippets included a button that toggled a state variable to show the infoPage, but upon clicking the button, the infoPage was not being displayed. Here’s an overview of the code in question:

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The button is integrated into a navigation bar, providing reusable templates for multiple views. However, despite implementing the interface and necessary functions, the infoPage variable would display an empty view when the modal was presented.

Understanding the Issue

The root cause of this problem lies in how the infoPage is initialized in the TrainingView protocol. Since the views need to conform to this protocol, the implementation of the infoPage must correctly return the appropriate view type. However, if a view doesn’t conform to the protocol correctly, the default implementation will kick in, which returns an empty view.

Code Breakdown

Here is the relevant portion of the TrainingView protocol:

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As you can see, the default implementation of infoPage returns an EmptyView() unless overridden in the conforming view.

The Solution

The solution to this problem is straightforward: Ensure that when you implement the infoPage, you are conforming to the protocol correctly by returning the appropriate view wrapped in an AnyView. Modify the implementation in ExerciseView like this:

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Key Takeaways:

Implement Protocols Correctly: Ensure that you correctly implement required properties in your conforming views.

Returning Proper Types: When passing views as parameters, wrap them in AnyView to ensure the type matches the expected parameter.

Debugging Modal Presentation: Use print statements or breakpoints to inspect the values of parameters passed in during runtime.

By following the above guidelines, your custom button will successfully display the modal with the desired view when clicked. Happy coding!