Скачать или смотреть Mastering SwiftUI: How to Effectively Use Completion Handlers in Button Actions

Discover how to implement `completion handlers` in SwiftUI Button actions to streamline your form submissions and enhance user experience.
---
This video is based on the question https://stackoverflow.com/q/63254909/ asked by the user 'squarehippo10' ( https://stackoverflow.com/u/5737391/ ) and on the answer https://stackoverflow.com/a/63255193/ provided by the user 'pawello2222' ( https://stackoverflow.com/u/8697793/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: SwiftUI - Can I use a completion handler in Button action?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Mastering SwiftUI: How to Effectively Use Completion Handlers in Button Actions

When working with SwiftUI, you might encounter scenarios where you need to perform an action before proceeding with the next step, especially in forms. For instance, if you want to retrieve a user's city and state using their zip code before saving their information, you will likely consider using a completion handler. However, it can sometimes be tricky to implement this correctly. Let's dive into a common question and explore the solution step by step.

The Problem

Imagine you have a form to collect a new user's name and zip code. When the user presses the "Save" button, you want to use Core Location to convert that zip code into the corresponding city and state. However, you find that your completion handler does not seem to activate as expected. Here's a simplified version of what you might be encountering:

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

Understanding Completion Handlers

Completion handlers are a way to execute code after a task is completed. They are particularly useful for asynchronous operations, such as network requests or geocoding. In your case, the goal is to ensure that once the city and state are retrieved, the form data can be saved without issues.

The Solution

To fix the problem, you need to ensure that the completion handler inside your getCityStateFromPostalCode function is called at the appropriate time, specifically after you have successfully retrieved the information. Here's how you can do this with your existing function:

Step 1: Modify the Function Signature

Ensure that your function signature includes the @ escaping keyword, which allows the closure to escape the lifetime of the function call. Here’s how it looks:

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

Step 2: Ensure Completion Handler is Called

It’s crucial to call completion() once you have the desired data. You can place this line after you've successfully retrieved the city and state. Note that you might want to handle errors as well by calling completion() in the error case with different parameters indicating a failure, if needed.

Final Implementation

Now, your button action and geocoding function should work seamlessly together. Once the geocoding is complete, you can save the user's information confidently. Here is a complete view of how it should look:

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

Conclusion

Implementing completion handlers in SwiftUI can greatly enhance the functionality of your applications, especially when dealing with asynchronous tasks. By ensuring that your handler is correctly called upon completion of tasks like geocoding, you can streamline processes like saving user data effectively.

Now that you understand how to properly utilize completion handlers in button actions, you can create more robust SwiftUI applications that handle user input seamlessly. Happy coding!