Скачать или смотреть How to Create a Custom SwiftUI Function that Returns a View and Accepts a Closure

Learn how to build a SwiftUI function that returns a view and accepts a closure for value changes, enabling data communication back to your parent view.
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This video is based on the question https://stackoverflow.com/q/66814350/ asked by the user 'ios coder' ( https://stackoverflow.com/u/13899957/ ) and on the answer https://stackoverflow.com/a/66814628/ provided by the user 'Ahmad' ( https://stackoverflow.com/u/12383844/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering SwiftUI: Create a Custom Function That Returns a View and Accepts a Closure

SwiftUI simplifies the process of building user interfaces but can sometimes raise questions about how to manage data flows efficiently. One common issue developers face is creating a function that not only returns a view but also accepts a closure for handling callbacks. In this post, we will explore how to implement such a function, allowing you to pass data changes from a child view back to the parent view.

The Problem at Hand

You might find yourself wanting a reusable SwiftUI function that allows you to observe and react to changes in a value. A classic example is when you're using state variables and need to act on their changes. Here’s a snippet of the original code that raises the question:

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In the above code, the perform function does not return change data back to ContentView. This makes it challenging to respond to data changes effectively.

The Solution: Adding a Callback Closure

The good news is that you can easily solve this by modifying your perform function. The solution involves adding a callback closure parameter to your function. Here’s how to do it:

Modify the perform function: Introduce a callback parameter that will act as the bridge for data back to the parent view.

Updated Code Example

Here’s the complete solution with the necessary modifications:

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Breakdown of the Changes

1. Adding the Callback

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By adding a callback parameter here, we allow the function to send data back once it detects changes.

2. Using the Callback

Inside the onPreferenceChange, we invoke the callback with newValue, thus enabling the value to be printed in the parent view.

Conclusion

With this updated approach, you can now effectively create reusable SwiftUI functions that allow data to be communicated back to the parent. This technique enhances your application’s interactivity and maintainability. You're now equipped to build more complex UIs in SwiftUI with greater confidence.

Remember, the key takeaway is to utilize closure callbacks, which enable efficient data management and responsiveness in your SwiftUI applications.

Happy coding! If you have any more questions about SwiftUI, feel free to leave a comment below.