* [ Michael Meeks <[EMAIL PROTECTED]>
* Wed, 26 Jun 2002 18:10:25 +0200 ]
> b) A way to handle delegates that is elegant; eg. I wish to
> implement the following (or similar):
>
> private void sizeAllocate (Widget w, Allocation a,
> Object closure);
> ...
> w.addHandler ("size_allocate", sizeAllocate, myObject);
>
> I don't mind doing a (redundant) new Foo (sizeAllocate), and
> I can see how you can do this with loads of delegates: new
> DelegateWidgetAllocation (sizeAllocate) eg. but I don't want to
> go around typing the method signature twice - once in declaring
> it, and once in a delegate allocation scheme.
You can use EventHandlerList if you find it more convenient:
private object SizeAllocateEvent = new object ();
private EventHandlerList _evList;
...
protected EventHandlerList Events
{
get {
if (_evList == null)
_evList = new EventHandlerList ();
return _evList;
}
}
public event EventHandler SizeAllocate
{
add { Events.AddHandler (SizeAllocateHAndler, value); }
remove { Events.RemoveHandler (SizeAllocateHAndler, value); }
}
void OnSizeAllocate (EventArgs e)
{
if (_events != null) {
EventHandler eh = (EventHandler) Events [SizeAllocateEvent]);
if (eh != null)
eh (this, e);
}
}
Now, to add an event, you do:
SizeAllocate += new EventHandler (your_method);
then you implement a subclass of EventArgs (is, SizeAllocattionArgs) that deals with
the arguments you need for the event.
public class SizeAllocationArgs : EventArgs
{
public SizeAllocationArgs (Widget w, Allocation a, object closure)
{
...
}
...
properties for accesing widget, allocation, ...
...
}
and now, to invoke the delegates:
OnSizeAllocate (new SizeAllocationArgs (w, a, closure));
and last, but not least:
public void your_method (object sender, EventArgs e)
{
SizeAllocationArgs s = e as SizeAllocationArgs;
if (s == null){
...
e was null or not an instance of
SizeAllocationArgs
...
}
....
}
Was something like this what you wanted?
If not, don't say that i haven't tried :)
Cheers!
- Gonzalo
--
Gonzalo Paniagua Javier <[EMAIL PROTECTED]>
http://www.gnome-db.org/~gonzalo/
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