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type
  TExampleMessageEvent = procedure(Sender: TObject; AMsg: string); of object;

  TExample = class(TThread)
  private
    FOnMessage: TExampleMessageEvent;
    FCurrentMessage: string;
    procedure SyncSendTextMessage();
    procedure SendTextMessage(AMsg: string);
  protected
    procedure Execute(); override;
  public
    constructor Create(AOnMessage: TExampleMessageEvent); reintroduce;
  end;

implementation

constructor TExample.Create(AOnMessage: TExampleMessageEvent);
begin
  FOnMessage := AOnMessage;
  inherited Create(False);
end;

procedure TExample.SyncSendTextMessage();
begin
  if Assigned(FOnMessage) then
    FOnMessage(FCurrentMessage);
end;

procedure TExample.SendTextMessage(AMsg: string);
begin
  FCurrentMessage := AMsg;
  Synchronize(SyncSendTextMessage);
end;

procedure TExample.Execute();
begin
  SendTextMessage('Test');
end;					

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if Assigned(PrintLine) then PrintLine(nil);