What is the point of security here...

By secure, I mean that public variable are visible to everything so they can easily be trampled on.


In load event, _screen.activeform is not formed yet, so it is not an object...

In my example, there are two forms. The first one has a grid on it and instantiates the second form. The code that grabs a reference to _Screen.activeForm is in the load of the second form, so _Screen.Activeform is definitely an object here. It is the first form.


also, oParent is a variable which need to be defined before use?!

No it does not. oParent is a form property that gets added using the form's AddProperty method. In VFP 8 and later there is also the ADDPROPERTY function.