InterruptiblePromise

Promises represent the eventual completion of an asynchronous operation.

A promise has one of three states, PromiseState, which can be obtained with InterruptiblePromise.State:

• PromiseState.Pending - The operation is still pending. The result of the operation isn't available yet.
• PromiseState.Done - The operation is complete, and a result is available.
• PromiseState.Cancelled - The operation has been cancelled.

An InterruptiblePromise starts in the PromiseState.Pending state and transitions to PromiseState.Done upon completion. If the Promise is cancelled using InterruptiblePromise.Cancel(), then its state may become PromiseState.Cancelled (see cancelling a Promise for caveats).

Obtaining results from a Promise

There are two ways of obtaining results from an InterruptiblePromise:

Polling a Promise

When the InterruptiblePromise is created, its PromiseState is set to PromiseState.Pending. You may poll the future using InterruptiblePromise.State to query the state of the asynchronous operation. When its state is PromiseState.Done, you may obtain the operation's result using InterruptiblePromise.Result.

Use a Unity Coroutine

Promises use a CustomYieldInstruction to facilitate Unity coroutines. Use yield return promiseInstance to pause execution of your coroutine. Unity will resume execution of your coroutine when InterruptiblePromise.State is no longer PromiseState.Pending.

public void CreatePromise()
{
   ResolveAnchorOnRooftopPromise rooftopPromise =
       AnchorManager.ResolveAnchorOnRooftopAsync(...);
   StartCoroutine(CheckRooftopPromise(rooftopPromise));
}
private IEnumerator CheckRooftopPromise(ResolveAnchorOnTerrainPromise promise)
{
   yield return promise;
   if (promise.State == PromiseState.Cancelled) yield break;
   var result = promise.Result;
   /// Use the result of your promise here.
}

Cancelling a Promise

You can try to cancel an InterruptiblePromise by calling InterruptiblePromise.Cancel(). Due to multi-threading, it is possible that the cancel operation is not successful, and any Unity coroutine may successfully resume execution regardless.

Details
Template Parameters	T The type of the async task result.

Summary

Inheritance

Inherits from: UnityEngine::CustomYieldInstruction

Properties
Result	T Gets the result, if the operation is done.
State	PromiseState Gets the PromiseState associated with this promise.

Public functions
Cancel()	void Cancels execution of this promise if it's still pending.

Properties

Result

T Result

Gets the result, if the operation is done.

State

PromiseState State

Gets the PromiseState associated with this promise.

Used to determine if the promise is still waiting for the result.

Public functions

Cancel

void Cancel()

Cancels execution of this promise if it's still pending.