| Re: objects and widgets [message #49236 is a reply to message #19933] |
Wed, 05 July 2006 06:21  |
btt
Messages: 345
Registered: December 2000
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Senior Member |
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gnarloo@libero.it wrote:
> Dear all, I havent been around for pretty a long time, anyway, hope you
> all are doing fine.
> Imagine a program with a gui interface and callback procedures.
> i am writing the callback procedures, (basically the core of the
> program) but one thing occurs. I am using objects (self made, i wrote
> structures and methods) and i create them with obj_new at the '
> beginning' of my program, that is, i create the objects in the realize
> callback procedure of the base_0 widget. when I try to use the objects
> i have created in another unit program, for example a mouse button
> procedure, the object appears as undefined. I know for sure that the
> object was created but it appears that it doesnt have global scope. can
> anyone help? thanx to all in advance.
>
Hi,
While objects are persistent heap variables they really don't have the
global scope you re assuming they do. You still have to tuck a reference
to the object somewhere handy in you program. Your best bet is to store
a reference to your objects in the UVALUE of the widget generating the
event. I like to store both the object reference and the method that I
want to call when the event occurs.
myWidgetID = WIDGET_SOMETHING(parent, ...., $
UVALUE = {OBJECT:myObjectReference, METHOD: "MethodForHandlingEvent"})
In the event callback access the the UVALUE that contains the reference
using (very simple example) ....
PRO MYEVENT, ev
WIDGET_CONTROL, ev.ID, get_Uvalue = myInfo
CALL_METHOD, myInfo.method, myInfo.object, ev
END
On the ATTVIS user contribution website there are some generic
object-associated event handlers written by Jim Pendelton that give you
more details. As always, check out David Fanning's very detailed
resources on this subject.
Cheers,
Ben
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