Скачать или смотреть How to Execute a Function After Another in Swift

Learn how to ensure one function executes after another in Swift using completion handlers. This post explains the solution step-by-step in an easy-to-understand way.
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How to Execute a Function After Another in Swift: A Complete Guide

In software development, you often encounter scenarios where you need to execute one function after another. Particularly in asynchronous programming with Swift, managing the flow of function execution can be tricky. A common situation is when you need to wait for a task, such as a network request, to finish before proceeding to the next step.

In this guide, we will explore how to implement this using completion handlers, enabling you to execute the werteEintragen() function only after the weatherManager.linkZusammenfuegen() function has successfully completed.

Understanding the Problem

In the code you provided, we have two functions:

linkZusammenfuegen(): This function performs a network request to get data.

werteEintragen(): This function updates the UI with the fetched data.

The issue arises because werteEintragen() gets executed before linkZusammenfuegen() finishes loading data. You are currently using a delay (with DispatchQueue) to wait for 2 seconds, which is not an ideal solution.

Solution: Using Completion Handlers

To solve this problem properly, we can use completion handlers. A completion handler lets you specify code that should be executed once a task finishes. Here’s how to set this up step by step:

Step 1: Modify linkZusammenfuegen()

Add a completion handler parameter to your linkZusammenfuegen() function, which will be invoked after the network request is completed.

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

Step 2: Modify perfromRequest()

Similarly, adjust your perfromRequest() function to accept a completion handler and call it based on the result of the network request.

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

Step 3: Update Your View Controller

Lastly, modify the view controller to use the updated linkZusammenfuegen() method with the completion handler:

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

Conclusion

Using completion handlers in Swift allows you to manage asynchronous tasks effectively, ensuring one function executes after another. In our case, this prevents premature UI updates until the necessary data has been retrieved.

By following the outlined steps, you can achieve a more robust flow in your application, improving user experience and code reliability.

Now you’re ready to implement this pattern in your Swift projects! Happy coding!