Promise equivalent in C#
In C#:
Task<T>
is a future (orTask
for a unit-returning future).TaskCompletionSource<T>
is a promise.
So your code would translate as such:
// var promise = new Promise<MyResult>;
var promise = new TaskCompletionSource<MyResult>();
// handlerMyEventsWithHandler(msg => promise.Complete(msg););
handlerMyEventsWithHandler(msg => promise.TrySetResult(msg));
// var myResult = promise.Future.Await(2000);
var completed = await Task.WhenAny(promise.Task, Task.Delay(2000));
if (completed == promise.Task)
; // Do something on timeout
var myResult = await completed;
Assert.Equals("my header", myResult.Header);
The "timed asynchronous wait" is a bit awkward, but it's also relatively uncommon in real-world code. For unit tests, I would just do a regular asynchronous wait:
var promise = new TaskCompletionSource<MyResult>();
handlerMyEventsWithHandler(msg => promise.TrySetResult(msg));
var myResult = await promise.Task;
Assert.Equals("my header", myResult.Header);
The rough C# equivalent without third-party libraries would be:
// var MyResult has a field `Header`
var promise = new TaskCompletionSource<MyResult>();
handlerMyEventsWithHandler(msg =>
promise.SetResult(msg)
);
// Wait for 2 seconds
if (promise.Task.Wait(2000))
{
var myResult = promise.Task.Result;
Debug.Assert("my header" == myResult.Header);
}
Note that it is usually best to use the await
/async
to as high a level as possible. Accessing the Result
of a Task
or using Wait
can in some cases introduce deadlocks.
You can use C# Promises library
Open sourced on Github: https://github.com/Real-Serious-Games/C-Sharp-Promise
Available on NuGet: https://www.nuget.org/packages/RSG.Promise/