Resolving Combine Issues: Making a URLSession Request in Swift

Описание: Learn how to successfully perform a `URLSession` request with Combine in Swift. Discover the common pitfall that causes network requests to fail, and how to fix it effectively.
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This video is based on the question https://stackoverflow.com/q/66972792/ asked by the user 'bruno' ( https://stackoverflow.com/u/516765/ ) and on the answer https://stackoverflow.com/a/66972903/ provided by the user 'Andrew' ( https://stackoverflow.com/u/5508175/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving Combine Issues: Making a URLSession Request in Swift

If you are working with Swift's Combine framework for reactive programming, you may encounter some challenges when trying to perform a URLSession request. One common issue developers face is that the request doesn't seem to execute properly, leading to nothing being printed on the console. In this post, we'll break down the problem and provide a simple yet effective solution.

The Problem

You might have written code similar to the following to fetch data from an API:

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While you might expect this code to fetch the user's repositories, you notice that nothing prints to the console. This usually happens because the repos variable goes out of scope immediately after the viewDidLoad method completes, effectively canceling the request before it can finish.

The Solution

To resolve this issue, you need to keep a reference to the AnyCancellable object that the sink method returns. This is crucial to ensure that your network request persists and is not cancelled prematurely. Here's how to modify your code:

Step 1: Import Combine

Make sure you have imported the Combine framework at the top of your Swift file:

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Step 2: Declare a Property for AnyCancellable

In your ViewController, declare a property to hold the AnyCancellable:

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Step 3: Update the viewDidLoad Method

Now, modify the viewDidLoad method to assign the request to the cancellable variable instead of creating it inline:

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Key Takeaways

Use AnyCancellable to hold on to your Combine requests.

Ensure that the cancellable property is retained beyond the scope of your function calls.

Watch out for the scope of your variables; going out of scope can cause requests to fail unexpectedly.

Conclusion

By following the steps outlined above, you can successfully make a URLSession request using Combine in Swift without encountering issues related to scope and cancellations. If you implement these changes and ensure the structure Repository is correctly defined to match the API response, you should see the expected output in your console.

Now you can confidently work with Combine to handle network requests in your Swift applications!