Скачать или смотреть How to Present an UIAlertController After Dismissing a View Controller in iOS

Learn how to efficiently present an `UIAlertController` in your iOS app immediately after dismissing a `View Controller` using Swift and Xcode.
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This video is based on the question https://stackoverflow.com/q/62344805/ asked by the user 'David' ( https://stackoverflow.com/u/9548591/ ) and on the answer https://stackoverflow.com/a/62345144/ provided by the user 'Jawad Ali' ( https://stackoverflow.com/u/1780632/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Presenting an Alert After Dismissing a View Controller in iOS

When developing iOS applications, you may encounter a scenario where you need to show an alert message right after dismissing a View Controller. This is a common requirement but can be tricky to implement if you're not familiar with the right techniques. In this post, we'll delve into how to present an UIAlertController after dismissing a View Controller using Swift and Xcode.

Understanding the Challenge

Suppose you've presented a View Controller, and after some user interaction (like sending a message), you want to dismiss that View Controller and instantly show an alert to the user confirming the action. The problem arises when you try to display the alert immediately after the dismissal code. The dismiss action completes before the alert is presented, resulting in the alert not displaying correctly.

Initial Code Example

Here's how you might be attempting to dismiss the View Controller and show an alert:

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This won’t work as expected because you're trying to present the alert on a now-dismissing View Controller. Now, let's explore the solution.

Solution Overview

To achieve this functionality, we use the completion handler of the dismiss method. The idea is to present the alert only after the dismissal is fully animated and completed. We also need a method to find the top-most view controller, as the alert needs to be presented on top of the currently visible view controller.

Step 1: Modify the Dismiss Method

We can modify the dismissal code to include a completion block where we’ll create and present the alert. Here’s how you can structure it:

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

Step 2: Create the Extension to Get the Top-most View Controller

To find the currently displayed view controller, we will create an extension for UIApplication. This helps us locate the top-most view controller, allowing us to present the alert without issues:

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

Explanation of the Code

Dismiss Method: We dismiss the current View Controller. Inside the completion block of the dismissal, we create an UIAlertController instance with a title and action button.

Top-most View Controller: This extension filters for the key window and traverses through any presented view controllers to get the one on top. This is where we will present the alert.

Conclusion

By following the steps outlined in this post, you can seamlessly present an UIAlertController immediately after dismissing a View Controller. This enhances user experience in your application by providing instant feedback on actions they perform. Remember to always use completion handlers in similar scenarios to ensure that your views are displayed at the right time.

With these techniques, you'll be well on your way to mastering UIViewController management in your iOS apps. Happy coding!