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Discover how to manage multiple asynchronous API requests in SwiftUI, ensuring that dependent requests are executed in the correct order.
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How to Handle SwiftUI Multiple API Requests: Ensuring Proper Order of Execution

As a beginner in SwiftUI, you may encounter issues when managing multiple asynchronous API calls, especially when one call depends on the data retrieved from another. If you find yourself in a situation where your second API request is executed before the first request has completed, don’t worry — you're not alone! This guide will explain the problem clearly and provide an effective solution so you can manage your API requests seamlessly in SwiftUI.

Understanding the Problem

When working with asynchronous functions, especially with network requests, each function does not wait for the previous one to finish before running. In the code snippet provided, we notice that method1 is called in the initializer, followed immediately by method2. This can lead to an error where method2 attempts to access data from programme before it has been populated with results from method1. The out of range error occurs because self.programme is still empty at the time method2 is called.

Issues with the Current Implementation

Asynchronous nature of network requests causes unpredictability in execution order.

Directly calling method2 in the initializer leads to attempts to access uninitialized data.

The Solution

To resolve the issue, we should ensure that method2 is called only after method1 has completely finished fetching and decoding data. This can be achieved by moving the call to method2 inside the completion handler of method1. Here's how to do it step-by-step:

Step-by-Step Implementation

Modify the Initializer: Remove the immediate call to method2 in the initializer.

Update method1: Call method2 inside the completion block after successfully setting self.programme.

Here is the modified code:

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

Key Takeaways

Restructure Calls: Ensure dependent methods are called in the completion handler or after the necessary data is set.

Error Handling: Always implement error handling in your API calls to better manage potential data issues.

Conclusion

Managing multiple API requests in SwiftUI can initially seem tricky, especially when they are interdependent. By ensuring that you call subsequent methods only after data is successfully retrieved and processed, you can avoid runtime errors and streamline your app's data flow. Remember to utilize good coding practices such as error handling, which can save you time and frustration down the road.

By following the steps outlined in this blog, you should be well on your way to mastering asynchronous networking in SwiftUI! If you have any questions or additional tips, feel free to share them in the comments below!