87 lines
3.0 KiB
C#
87 lines
3.0 KiB
C#
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namespace UnityEngine.XR.ARSubsystems
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{
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/// <summary>
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/// A Promise is used for operations that retrieve data asynchronously. Use this object
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/// to determine the status of the operation (that is, whether it has completed), and
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/// the resulting data.
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/// </summary>
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/// <remarks>
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/// Since <see cref="Promise{T}"/> derives from <c>CustomYieldInstruction</c>,
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/// you can <c>yield return</c> on a Promise in a coroutine. If you prefer not
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/// to use the Promise as a coroutine, you can manually check <see cref="Promise{T}.keepWaiting"/>
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/// to determine if the operation has completed. Once the operation is complete, you can get the
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/// resulting value from <see cref="Promise{T}.result"/>.
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/// </remarks>
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/// <example>
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/// Example usage in a coroutine:
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/// <code>
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/// IEnumerator MyCoroutine()
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/// {
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/// var promise = GetDataAsync();
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/// yield return promise;
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/// Debug.LogFormat("Operation complete. Result = {0}", promise.result);
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/// }
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/// </code>
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/// </example>
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/// <typeparam name="T">The type of information the asynchronous operation retrieves.</typeparam>
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public abstract class Promise<T> : CustomYieldInstruction
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{
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/// <summary>
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/// Will return <c>true</c> as long as the operation has not yet completed.
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/// </summary>
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public override bool keepWaiting
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{
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get
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{
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OnKeepWaiting();
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return !m_Complete;
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}
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}
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/// <summary>
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/// The result of the asynchronous operation.
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/// Not valid until <see cref="keepWaiting"/> returns <c>false</c>.
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/// </summary>
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public T result { get; private set; }
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/// <summary>
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/// Creates a resolved promise (that is, a promise that is already complete).
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/// </summary>
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/// <param name="result">The result of the operation.</param>
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/// <returns>A completed <see cref="Promise{T}"/>.</returns>
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public static Promise<T> CreateResolvedPromise(T result)
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{
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return new ImmediatePromise(result);
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}
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/// <summary>
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/// The creator of the <see cref="Promise{T}"/> should call this
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/// when the asynchronous operation completes.
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/// </summary>
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/// <param name="result">The result of the asychronous operation.</param>
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protected void Resolve(T result)
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{
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this.result = result;
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m_Complete = true;
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}
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/// <summary>
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/// Invoked whenever <see cref="keepWaiting"/> is queried.
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/// Implement this to perform per-frame updates.
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/// </summary>
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protected abstract void OnKeepWaiting();
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bool m_Complete;
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class ImmediatePromise : Promise<T>
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{
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protected override void OnKeepWaiting() { }
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public ImmediatePromise(T immediateResult)
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{
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Resolve(immediateResult);
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}
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}
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}
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}
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