procedure TForm1.N5Click(Sender: TObject);
begin
 if application.FindComponent('fomr5')=nil then
   begin
      application.CreateForm(tform5,form5);
      form5.show;
   end;
end;

引言: 一個MDI的專案，若裡面有N個子表單，每當選擇一個表單時時，就要寫一段程式判斷表單是否已建立，想問看看是否有更簡易的方法。 例.有n個表單，則下面程式就要寫n次@@

procedure TForm1.N5Click(Sender: TObject);
begin
 if application.FindComponent('fomr5')=nil then
   begin
      application.CreateForm(tform5,form5);
      form5.show;
   end;
end;

procedure TForm1.NewForm(FormClass: TFormClass; Form: TForm; Name : String);
begin
  Form := TForm(application.FindComponent(Name));
  if not Assigned(Form) then
    application.CreateForm(FormClass,Form);
  Form.show; // always show it
end;    procedure TForm1.Form21Click(Sender: TObject);
begin
  NewForm(TForm2,Form2,'Form2');
end;    procedure TForm1.Form31Click(Sender: TObject);
begin
  NewForm(TForm3,Form3,'Form3');
end;

procedure TForm1.NewForm(FormClass: TFormClass; Form: TForm);
var i : integer;
begin
  for i := 0 to Screen.FormCount - 1 do
    if Screen.Forms[i] is FormClass then
    begin
      Form := Screen.Forms[i];
      break;
    end;
  if not Assigned(Form) then
    application.CreateForm(FormClass,Form);
  Form.show; // always show it
end;
 
procedure TForm1.Form21Click(Sender: TObject);
begin
  NewForm(TForm2,Form2);
end;
 
procedure TForm1.Form31Click(Sender: TObject);
begin
  NewForm(TForm3,Form3);
end;