delphi - 访问 OmniThread 并行任务中的参数会中止任务

Question

在使用OmniThread库创建并行任务的程序中，当我尝试访问并行任务中的参数时，参数访问之后的代码没有执行，因此显然任务中止：

uses
  System.SysUtils, System.Classes,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,

  OtlComm, OtlTask, OtlTaskControl, OtlEventMonitor;

type
  TForm1 = class(TForm)
    btnStartOTLTask: TButton;
    OTLMonitor: TOmniEventMonitor;
    procedure btnStartOTLTaskClick(Sender: TObject);
    procedure OTLMonitorTaskMessage(const task: IOmniTaskControl; const msg:
        TOmniMessage);
  private
    { Private-Deklarationen }
    FTestTask: IOmniTaskControl;
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ Place a TOmniEventMonitor component on the form,
  name it OTLMonitor
  and implement the OnTaskMessage event-handler: OTLMonitorTaskMessage }

procedure TestParameters(const ATask: IOmniTask);
var
  test: Integer;
begin
  ATask.Comm.Send(16); // does execute
  test := ATask.Param['From']; // ?? <<<===========================
  ATask.Comm.Send(17); // does NOT execute!
end;

procedure TForm1.btnStartOTLTaskClick(Sender: TObject);
begin
  if not Assigned(FTestTask) then // prevent multiple tasks
    FTestTask := CreateTask(TestParameters, 'TestParameters')
                   .MonitorWith(OTLMonitor)
                   .SetParameters(['From', 0, 'To', 99])
                   .Run
  else
    MessageDlg('Task is already running!', mtInformation, [mbOK], 0);
end;

procedure TForm1.OTLMonitorTaskMessage(const task: IOmniTaskControl; const msg: TOmniMessage);
begin
  Self.Caption := IntToStr(msg.MsgID);
end;

那么访问参数有什么问题'From'呢？

Answer 1

我找到了一种解决方法：

procedure TestParameters(const ATask: IOmniTask);
begin
  // this does work:
  ATask.Comm.Send(ATask.Param.ByName('From'));
  ATask.Comm.Send(ATask.Param.ByName('To'));

  // ALSO this does work:
  ATask.Comm.Send(ATask.Param['From']);
  ATask.Comm.Send(ATask.Param['To']);
end;

procedure TForm1.btnStartOTLTaskClick(Sender: TObject);
begin
  if not Assigned(FTestTask) then // prevent multiple tasks
    FTestTask := CreateTask(TestParameters, 'TestParameters')
                   .MonitorWith(OTLMonitor)
                   // SetParameters does not work:
                   //.SetParameters(['From', 1, 'To', 99])
                   // this does work:
                   .SetParameter('From', 1)
                   .SetParameter('To', 99)
                   .Run
  else
    MessageDlg('Task is already running!', mtInformation, [mbOK], 0);
end;

procedure TForm1.OTLMonitorTaskMessage(const task: IOmniTaskControl; const msg: TOmniMessage);
begin
  Memo1.Lines.Add(IntToStr(msg.MsgID));
end;

procedure TForm1.OTLMonitorTaskTerminated(const task: IOmniTaskControl);
begin
  FTestTask := nil;
  Memo1.Lines.Add('Task terminated');
end;