Example with progress Bar on ForEach abstraction.
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unit test_55_ForEachProgress; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ComCtrls, OtlTask, OtlParallel; type TfrmForEachWithProgressBar = class(TForm) btnStart : TButton; pbForEach: TProgressBar; procedure btnStartClick(Sender: TObject); private FPosition: integer; FProgress: integer; FWorker : IOmniParallelLoop<integer>; procedure IncrementProgressBar; end; var frmForEachWithProgressBar: TfrmForEachWithProgressBar; implementation {$R *.dfm} const CNumLoop = 20000; procedure TfrmForEachWithProgressBar.btnStartClick(Sender: TObject); begin btnStart.Enabled := false; pbForEach.Max := 100; pbForEach.Position := 0; pbForEach.Update; FProgress := 0; FPosition := 0; // reference must be kept in a global field so that the task controller is not destroyed before the processing ends FWorker := Parallel .ForEach(1, CNumLoop) .NoWait // important, otherwise message loop will be blocked while ForEach waits for all tasks to terminate .OnStop( procedure (const task: IOmniTask) begin // because of NoWait, OnStop delegate is invoked from the worker code; we must not destroy the worker at that point or the program will block task.Invoke( procedure begin FWorker := nil; btnStart.Enabled := true; end ); end ); FWorker.Execute( procedure (const task: IOmniTask; const i: integer) begin // do some work Sleep(1); // update the progress bar // we cannot use 'i' for progress as it does not increase sequentially // IncrementProgressBar uses internal counter to follow the progress task.Invoke(IncrementProgressBar); end ); end; procedure TfrmForEachWithProgressBar.IncrementProgressBar; var newPosition: integer; begin Inc(FProgress); newPosition := Trunc((FProgress / CNumLoop)*pbForEach.Max); // make sure we don't overflow TProgressBar with messages if newPosition <> FPosition then begin pbForEach.Position := newPosition; FPosition := newPosition; end; end; end. |