Class Promise<T>
A Promise is used for operations that retrieve data asynchronously. Use this object to determine the status of the operation (that is, whether it has completed), and the resulting data.
Inherited Members
Namespace: UnityEngine.XR.ARSubsystems
Syntax
public abstract class Promise<T> : CustomYieldInstruction, IEnumerator
Type Parameters
Name | Description |
---|---|
T | The type of information the asynchronous operation retrieves. |
Remarks
Since Promise<T> derives from CustomYieldInstruction
,
you can yield return
on a Promise in a coroutine. If you prefer not
to use the Promise as a coroutine, you can manually check keepWaiting
to determine if the operation has completed. Once the operation is complete, you can get the
resulting value from result.
Examples
Example usage in a coroutine:
IEnumerator MyCoroutine()
{
var promise = GetDataAsync();
yield return promise;
Debug.LogFormat("Operation complete. Result = {0}", promise.result);
}
Properties
keepWaiting
Will return true
as long as the operation has not yet completed.
Declaration
public override bool keepWaiting { get; }
Property Value
Type | Description |
---|---|
Boolean |
Overrides
result
The result of the asynchronous operation.
Not valid until keepWaiting returns false
.
Declaration
public T result { get; }
Property Value
Type | Description |
---|---|
T |
Methods
CreateResolvedPromise(T)
Creates a resolved promise (that is, a promise that is already complete).
Declaration
public static Promise<T> CreateResolvedPromise(T result)
Parameters
Type | Name | Description |
---|---|---|
T | result | The result of the operation. |
Returns
Type | Description |
---|---|
Promise<T> | A completed Promise<T>. |
OnKeepWaiting()
Invoked whenever keepWaiting is queried. Implement this to perform per-frame updates.
Declaration
protected abstract void OnKeepWaiting()
Resolve(T)
The creator of the Promise<T> should call this when the asynchronous operation completes.
Declaration
protected void Resolve(T result)
Parameters
Type | Name | Description |
---|---|---|
T | result | The result of the asychronous operation. |