[Gambas-user] Event and inheritance

[Benoit Minisini]

On Thursday 03 February 2005 14:21, Eric Lemasson wrote:
> Hi all,
>
> I have just discovered Gambas one week ago so please excuse my dummy
> question ....
>
> I have created a sub-class of TextArea and I want to define a global
> behavior for all instances of this class for the Event change.
> How can I trap and redefine the event of a parent class in a sub-class ?
>
> I have tried to define some function like MyTextArea_Change or
> _Change, but do not work.
>
> Any help greatly appreciated.
>
> Thanks
>

You can't trap an event generated by a class in an inherited class, it is a 
non-sense :-) 

Event are generated by objects, not classes and are sent to their event 
observer.

You must replace inheritance by composition: create a MyTextArea class that 
instanciate a TextArea in its constructor, and this way you will receive all 
events generated by the TextArea. But if you want the MyTextArea event 
observer to catch other events from TextArea, you must reimplement all of 
them.

MyTextArea.class:
...
EVENT KeyPress
PRIVATE hTextArea AS TextArea
...
PUBLIC SUB _new(Parent AS Container)
  hTextArea = NEW TextArea(Parent) AS "TextArea"
  ...
END

PUBLIC SUB TextArea_KeyPress()
  RAISE KeyPress
END 

If you want to handle the Change event for a group of TextArea, use the 
(Group) pseudo-property in the properties sheet.

Do you get it ? :-)

-- 
Benoit Minisini
mailto:gambas at ...1...