In both case you've described,I fully understood the poit.My problem is that in the designer I create a button ,and I gave it a name (in column "variable/id?") *btnOK*.Then I change to head file and cpp file where there is no such a variable named btnOK inside the entire file,no only any classes,so how can I call
btnOK=callback(btnOKClick);//where is variable *btnOK*?