Ian
You wrote in message
news:_xE97.14438$
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> ...
> I ran the BeeGrid control through the ActiveX component wizard and have
got
> a load of BeeGrid..... subclasses under IDispatch that match the
interfaces
> in the control's documentation, I assume this is what's meant by
"generating
> the interface".
Yes.
> I've created a view and a presenter to hold the control which I can then
> show and invoke method's on it. My problem is that when I handle an event
> (in the presenter) that should pass say a RowBuffer
> (BeeGridOLEDB10IsgRowBuffer exists under IDispatch) I actually get an
> IDispatch object that has a typeInfo of "a
> TKindInterfaceAnalyzer('IsgRowBuffer')". I don't see how I should then use
> this IDispatch object in place of the BeeGridOLEDB10IsgRowBuffer that I
was
> expecting to receive.
Active-X event interfaces (also called "source" interfaces) are normally
implemented as dispinterfaces, i.e. as raw IDispatch, because VB had (has?)
a limitation that it could only implement IDispatch based event interface.
This is not fundamental to event interfaces, but it is almost universally
the case that they are pure dynamic dispatch (not vtbl extension with typed
methods). This means the events are received through IDispatch::Invoke(),
and so the argument types are restricted to those supported inside a
VARIANT. Cutting a long story short this means that any "interface"
arguments passed to the event handle will be of generic IDispatch type. You
can convert these to their more specialised/concrete type by sending them
#asImplType, which will attempt a down cast where possible. The system does
not do this by default because it relies on type information and is a
relatively costly thing to do should the argument not be used (there may be
no observers or the handlers may ignore the argument). You can also use
#queryInterface: to query off the interface you are expecting, which does
not rely on the availability of type information and is quicker.
Regards
Blair
Locked
