AsyncAwait

异步

该库（Delphi 10或更高版本）揭示了使用COM基础架构（ ICOntextCallback.ContextCallback ）在.NET中的任务和任务对象的宽松等效物，以同步主要或任何任意线程上的持续调用。在VC ++中，异步/等待中的co_await中使用了相同的API。该库在EXE和DLL项目中都可以使用，并且（与TThread.synchornize不同）不依赖于签名的呼叫来检查。

源代码是根据MIT许可证的。

要使用此库，请在使用条款上添加异步。然后，您可以如下创建代码：

 procedure TForm1.btnFibonacciClick (Sender: TObject);
var
  seed: UInt64;
begin
  seed := Random(MaxInt);
  lblResult.Caption := Format( ' Calculating Fibonacci number for %d. Please wait... ' , [seed]);
  TTask<UInt64>.Async(
              // timeconsuming call on a secondary thread
              function : UInt64
              begin
                Result := Fibonacci(seed);
              end ,
              // update the UI on the main thread
              procedure(task : ITask<UInt64>; Value : UInt64)
              begin
                if task.Status = TTaskStatus.RanToCompletion
                  then lblResult.Caption := Format( ' Fibonacci number for %d is %d ' , [seed, Value ])
                else if task.Status = TTaskStatus.Faulted
                  then lblResult.Caption := Format( ' Error calculating Fibonacci number: %s ' , [task.Exception.Message])
              end ,
              // tell to continue on the main thread -
              // don't need to specify this parameter as it defaults to true anyway
              true
              );
end ;

即使您在辅助线程上启动新任务，也可以指定特定的同步上下文：

 procedure TForm1.Button1Click (Sender: TObject);
var
  t : ITask<integer>;
  syncContext : ISynchronizationContext;
begin
  syncContext := TSynchronizationContext.Current;

  t := TTask<integer>.Async(

              // async function
              function() : integer
              var
                delay : integer;
              begin
                delay := Random( 10000 );
                sleep(delay);
                Result := delay;
                // run another task
                // start it explicitly since we need to configure the
                // synchornization context (main thread) first
                // before the continuation code has a chance to run
                TTask.Create(
                     procedure()
                     begin
                       sleep( 2000 );
                     end
                   ).
                   ContinueWith(
                     procedure(task : ITask)
                     begin
                       ShowMessage( ' Done second task ' );
                     end ,
                     // use the sync context from the main thread since we are showing a window
                     syncContext
                     ).
                   // now start the task after we configured it
                   Start;
              end ,

              // continue with
              // it is guaranteed to run on the calling thread (this main thread)
              // since continueOnCapturedContext parameter defaults to true
              procedure(task : ITask<integer>; Value : integer )
              begin
                if task.Status = TTaskStatus.RanToCompletion
                  then ShowMessage(Format( ' All done after sleeping for %d seconds ' , [task. Value div 1000 ]))
                else if task.Status = TTaskStatus.Faulted
                  then ShowMessage(Format( ' Task faulted. Exception type = %s: %s ' , [task.Exception.ClassName, task.Exception.Message]))
              end ,
              // continue on the main thread - don't need to specify this parameter as it defaults to true
              true
                );
  if t.Wait( 2000 )
    then ShowMessage(Format( ' Done after waiting for less than 2 seconds. Task returned %d ' , [t. Value ]))
    else ShowMessage( ' Still not done after waiting for 2 seconds ' );
end ;