IdThreadComponent (Indy 9) in Delphi 2007 Error-CodePudding

I'm using IdTCPClient and IdThreadComponent to get some information for a barcode reader. This code, with some changes is working in Delphi 11 and Indy 10 but not in Delphi 2007 and Indy 9:

procedure TPkgSendF1.IdThreadComponent1Run(Sender: TIdCustomThreadComponent);
var
  s: String;
begin
  s := IdTCPClient1.ReadLn('&', 20000, 1500);
  TThread.Queue(nil, procedure  // <== Expected @ but received PROCEDURE
                begin
                  ProcessRead(s);
                end);
end;

// [DCC Error] PkgSendF1.pas(239): E2029 Expression expected but 'PROCEDURE' found

procedure TPkgSendF1.ProcessRead(AValue: string);
begin
  Memo1.Text := AValue;
end;

If I don't use the TThread.Queue I miss some readings. I'll appreciate any help. Francisco Alvarado

CodePudding user response：

Anonymous methods did not exist yet in Delphi 2007, they were introduced in Delphi 2010. As such, TThread.Queue() in D2007 only had 1 version that accepted a TThreadMethod:

type
  TThreadMethod = procedure of object;

Which means you need to wrap the call to ProcessRead() inside a helper object that has a procedure with no parameters, eg:

type
  TQueueHelper = class
  public
    Caller: TPkgSendF1;
    Value: String;
    procedure DoProcessing;
  end;

procedure TQueueHelper.DoProcessing;
begin
  try
    Caller.ProcessRead(Value);
  finally
    Free;
  end;
end;

procedure TPkgSendF1.IdThreadComponent1Run(Sender: TIdCustomThreadComponent);
var
  s: string;
begin
  s := IdTCPClient1.ReadLn('&', 20000, 1500);
  with TQueueHelper.Create do
  begin
    Caller := Self;
    Value := s;
    TThread.Queue(nil, DoProcessing);
  end;
end;

FYI, Indy (both 9 and 10) has an asynchronous TIdNotify class in the IdSync unit, which you can use instead of using TThread.Queue() directly, eg:

uses
  IdSync;

type
  TMyNotify = class(TIdNotify)
  public
    Caller: TPkgSendF1;
    Value: String;
    procedure DoNotify; override;
  end;

procedure TMyNotify.DoNotify;
begin
  Caller.ProcessRead(Value);
end;

procedure TPkgSendF1.IdThreadComponent1Run(Sender: TIdCustomThreadComponent);
var
  s: string;
begin
  s := IdTCPClient1.ReadLn('&', 20000, 1500);
  with TMyNotify.Create do
  begin
    Caller := Self;
    Value := s;
    Notify;
  end;
end;