Differences in dynamic creation of an object

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#1 by (8 votes)

4

When I create an object dynamically, for example a form, I do this:

Formulario := TFormulario.Create(nil);  
try  
    Formulario.ShowModal;  
finally  
    Formulario.Free;  
end;

What's the difference in creating an object by passing the following values to the AOwner parameter in the Create method?

Formulario := TFormulario.Create(Application);  
Formulario := TFormulario.Create(nil);  
Formulario := TFormulario.Create(Self);

delphi delphi-7

asked by anonymous 03.04.2014 / 22:22

1 answer

score 8 · Accepted Answer

The difference is who owns the window. That is, if the "owner" is deallocated, all forms that own this form as owner are also deallocated.

In the first example, form is only deallocated if the entire application is also. This is not strongly recommended because of performance issues because notifications passed to Application take a longer time to process;
In the second, form has no owner, ie the programmer should control the deallocation of this form ;
In the third, the form belongs to the screen that called it. Recommended for calling-screen modes.