# Posts

· 2018-01-25 · * * * *

## Async-Await instead of coroutines in Unity 2017

From http://www.stevevermeulen.com/index.php/2017/09/using-async-await-in-unity3d-2017/

Using coroutines in Unity is often a great way to solve certain problems, however it comes with certain drawbacks as well:

• Coroutines can’t return values. This encourages programmers to create huge monolithic coroutine methods instead of composing them out of many smaller methods. Some workarounds exist, such as passing a callback parameter of type Action<> to the coroutine, or casting the final untyped value that is yielded from the coroutine after it completes, but these approaches are awkward to use and error prone.
• Coroutines make error handling difficult. You cannot put a yield inside a try-catch, so it is not possible to handle exceptions. Also, when exceptions do occur the stack trace only tells you the coroutine where the exception was thrown, so you have to guess which other coroutines it might have been called from.

With the release of Unity 2017, it is now possible to use a new C# feature called async-await for our asynchronous methods instead. This comes with a lot of nice features compared to coroutines.

To enable this feature, all you need to do is open your player settings (Edit -> Project Settings -> Player) and change “Scripting Runtime Version” to “Experimental (.NET 4.6 Equivalent).

Let’s look at a simple example. Given the following coroutine:

public class AsyncExample : MonoBehaviour
{