Скачать или смотреть Resolving the suspension functions can be called only within coroutine body Error in Kotlin

Learn how to effectively fix the Kotlin error regarding suspension functions. This guide provides clarity on proper coroutine usage and avoids common pitfalls.
---
This video is based on the question https://stackoverflow.com/q/69443034/ asked by the user 'Cristobal BL' ( https://stackoverflow.com/u/14049806/ ) and on the answer https://stackoverflow.com/a/69443552/ provided by the user 'broot' ( https://stackoverflow.com/u/448875/ ) 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: kotlin error - suspension functions can be called only within coroutine body

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.
---
Understanding the Kotlin Error: Suspension Functions Can Be Called Only Within Coroutine Body

If you’re new to Kotlin, you might encounter some tricky errors, especially when dealing with asynchronous programming and coroutine functions. One common pitfall is encountering the error message "suspension functions can be called only within coroutine body". This can be confusing, especially when you're still getting the hang of how Kotlin and its coroutines work. In this post, we will break down this issue, explain why it occurs, and guide you through an effective solution.

The Scenario: Code Overview

In your MainActivity.kt file, you have a suspend function getTokenAsync() designed to fetch a token asynchronously. You are calling this function from another suspend function, handleLoadWebView(). Here's a simplified version of the code you're working with:

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

Your issue arises at the line where you try to call getTokenAsync() inside of async {}.

Why Does This Error Occur?

The root cause of the error is how you're attempting to use coroutines and suspend functions together:

Suspend Function Misuse: Both getTokenAsync() and handleLoadWebView() are suspendable, meaning you can call one within the context of the other without needing to wrap them in additional constructs like runBlocking().

Unnecessary Complexity: Using async { getTokenAsync() } to immediately await() it makes no sense and leads to unnecessarily complicated code. Since getTokenAsync() is a suspend function, you can call it directly instead.

Understanding Coroutine Context: The Kotlin coroutine builders (async, launch, etc.) allow you to perform asynchronous work in a cleaner manner, but they must be used correctly and in the right context.

The Solution: Simplifying Your Code

To address the problem at hand, you can simplify your handleLoadWebView() function. Instead of using runBlocking() and unnecessary async calls, directly call your getTokenAsync() function within the coroutine. Here’s how your revised code might look:

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

Key Changes Made:

Direct Call: getTokenAsync() is invoked directly without wrapping it inside async {}. This not only eliminates the error but also makes the code more straightforward.

Removed runBlocking(): By eliminating runBlocking(), you maintain a non-blocking operation, which is a best practice in coroutine usage.

Conclusion

The error "suspension functions can be called only within coroutine body" can be resolved by understanding how suspend functions work in Kotlin. By simplifying your code, you can effectively avoid the pitfalls of unnecessary complexity. Remember, when working with suspended functions, always consider calling them directly within the coroutine context without additional blocking constructs.

Happy coding with Kotlin, and may your asynchronous adventures be smooth!