Скачать или смотреть Why URLSession Doesn't Call Your API: Solving Common Problems in Swift

Discover why your `URLSession` isn't calling your API as expected and learn how to refactor your code for better results in Swift.
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This video is based on the question https://stackoverflow.com/q/64456797/ asked by the user 'raaamonnn' ( https://stackoverflow.com/u/11694568/ ) and on the answer https://stackoverflow.com/a/64457791/ provided by the user 'Paulw11' ( https://stackoverflow.com/u/3418066/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Why Your URLSession Doesn't Call the API

If you've been tinkering with Swift and the various libraries it has to offer, you might have faced an issue where your URLSession seems to work flawlessly in the Playground but fails to call your API in your main project. This can be frustrating, especially when everything appears to be set up correctly.

In this guide, we will dive deeply into this problem and provide a structured solution. We’ll walk you through an easy-to-understand breakdown, so you’ll be ready to tackle any issues concerning URLSession and asynchronous operations in Swift!

The Problem: URLSession Not Calling the API

The specific issue here is that your URLSession.shared.dataTask does not seem to invoke the completion block when you run the code in your main project. Below is a simplified version of the problematic code:

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Symptom of the Problem

The do block never executes, which implies that there's an issue with how the asynchronous data task is set up.

This leads us to explore the underlying cause of the issue.

The Solution: Refactoring Your Code

Improper Use of DispatchGroup

One significant problem in your code is the incorrect use of DispatchGroup. Here's what you need to understand about DispatchGroup:

Enter: Call this method before starting your asynchronous work.

Leave: Call this method once the task is complete.

In the current scenario, you don’t truly require a DispatchGroup. Instead, it's better to embrace the asynchronous nature of your API call.

A Better Approach: Using a Completion Handler

To solve this issue effectively, you can refactor the getWords function to utilize a completion handler. This lets your function notify your code when it receives the results, whether successful or not.

Here’s the rewritten code snippet employing a completion handler:

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

Calling the Function with the Completion Handler

Once you have transformed your function, you call it as follows:

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

Conclusion: Embrace Asynchronous Operations

By restructuring the getWords function to include a completion handler, you allow the app to operate asynchronously without locking the main thread. This approach enhances not only the performance but also the reliability of your network calls.

To summarize, when working with APIs in Swift:

Understand the asynchronous nature of network requests.

Utilize completion handlers to handle results properly.

Always manage optional values cautiously to prevent runtime errors.

Now you're well-equipped to make your API calls with ease and confidence. Happy coding!