Скачать или смотреть How to Invalidate CADisplayLink with a UIButton in iOS Development

Learn how to properly invalidate a CADisplayLink using a UIButton in your iOS applications, avoiding common errors and improving your understanding of Swift.
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This video is based on the question https://stackoverflow.com/q/65187278/ asked by the user 'VC25P' ( https://stackoverflow.com/u/10230680/ ) and on the answer https://stackoverflow.com/a/65189537/ provided by the user 'SuperTully' ( https://stackoverflow.com/u/14255478/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding CADisplayLink and UIButton Interaction in iOS

As a beginner in iOS development, you might often encounter challenges while managing the interactions of various components, especially when dealing with animations or refresh rates in your app. One common scenario involves using CADisplayLink, a class that allows you to synchronize your drawing code to the refresh rate of the display. But what if you want to invalidate this display link through a UIButton when it's no longer needed? This guide will guide you through that process step-by-step.

The Problem at Hand

You might be defining a CADisplayLink within a function but find yourself unable to access it later, specifically in an action connected to a UIButton. This leads to an error: ‘cannot find in scope’. Essentially, the display link is initialized locally, making it inaccessible from other parts of your class. Let's look at how to resolve this issue.

The Solution

To invalidate CADisplayLink successfully when a button is pressed, you should declare the display link as a property of your class rather than initializing it only within a function. Follow these steps:

Step 1: Declare the CADisplayLink as a Property

Instead of declaring the display link inside the function, declare it as an optional property at the class level:

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

Step 2: Initialize the Display Link

Now that you have a class-level property, you can initialize it in the method myDisplayLink as shown. This sets up the display link correctly:

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

Step 3: Invalidate the Display Link in UIButton Action

Finally, you can invalidate the display link from a UIButton action. This can be done simply by using the invalidate() method on your displayLink property inside your button’s action method:

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

Summary of the Solution

Declare: Define CADisplayLink as a property of your class rather than within a function.

Initialize: Set it up in your custom function, allowing it to be accessible throughout the class.

Invalidate: Use the invalidate() method in your UIButton action to stop the display link when needed.

Conclusion

Managing CADisplayLink in your iOS applications doesn’t have to be a daunting task. By following the above steps, you can easily control when it runs and when it stops, ensuring your app runs efficiently and without unnecessary outputs. Remember, proper scope and access management are key to effective coding practices. Happy coding!