如何在每两个不同的类上一起触发事件

Posted 2023-02-23

【中文标题】如何在每两个不同的类上一起触发事件

【英文标题】：How to trigger the event together on each two deferent class

【发布时间】：2011-02-25 19:59:12

【问题描述】：

我在一个单元上有两个对象类，是否可以触发这两个事件？假设触发了 FIRSTCLASS 事件，那么 SECONDCLASS 也会触发吗？

假设......

//Class 1-------------------------------------------------------------
type
   TOnEventTrigger = procedure(Sender : Tobject; Value :integer); 
   TMyFirstClass = Class(Tcomponent)
   private
      ....
   public
      ....
      propert OnEventTrigger : TOnEventTrigger read Fevent write Fevent;
   end;

procedure TMyFirstClass.FEvnt(Sender : Tobject; Value :integer); 
begin
    // here is normaly triggers the event //
    if Assigned(OnEventTrigger) then
       OnEventTrigger(Self,FSomevalue);

    // POSTMessage(GetForegroundWindow,WM_USER+3,0,0);
    // this is what i did here to get the result of FSomevalue
    // but this is not ideal. It work only on focus window.

end;

//Class 2-------------------------------------------------------------

type
   TOnEventTrigger = procedure(Sender : Tobject; Value :integer); 
   TMySecondClass = Class(Tobject)
   private
      ....
   public
      ....
      property OnEventTrigger : TOnEventTrigger; read Fevent write Fevent;
   end;

procedure TMySecondClass.FEvnt(Sender : Tobject; Value :integer); 
begin
    // I wanted here to trigger, whenenver the above is fired //
    if Assigned(OnEventTrigger) then
       OnEventTrigger(Self,FSomevalue);
end;

【参考方案1】：

您可以在创建两个类时将相同的事件处理程序分配给它们（伪代码）：

Form1 = class()
private
   ... 
protected
  A : TMyFirstClass;
  B : TMySecondClass;
  procedure MyHandler(Sender: TObject; Value: Integer);
end;

procedure Form1.CreateForm();
Begin
      Create A & B 
     A := TMyFirstClass.Create(Self);
     B := TMySecondClass.Create(Self);

      Assign Event Handler to both classes 
     A.OnEventTrigger := MyHandler;
     B.OnEventTrigger := MyHandler;
End;

procedure Form1.MyHandler(Sender: TObject; Value: Integer);
Begin
     ShowMessage('Event from '+Sender.ClassName+'. Value='+IntToStr(Value));
End;

这样，当事件从任一类触发时，它都会在 MyHandler() 代码中结束。