Get iEnumerator from nodelist

[Edwin Knoppert]

I am trying to get me the nodes via the enumerator.
problem is that the nodelist object is a late bound object.
So i was trying to use the interface pointer -4 to call the enumvariant interface.
Frankly i find the hard offsets a poor design.
Any luck i can keep using the late bound object and fetch me the enumerator anyway?
The enumerator is declared (early binding)

I seen code using Queryinterface but does not return an object:

    Local oUnk  As IUnknown    
    Local pEnum As Dword
    oUnk = oNodeList    
    oUnk.QueryInterface( $IID_IEnumVARIANT, pEnum ) To hr

[Michael Mattias]

Maybe pEnum needs to be defined as a PTR variable type?

As written, the compiler would pass a ptr to a DWORD, not a ptr to a ptr as required for iUnknown.queryInterface

[Edwin Knoppert]

I just found out that i misinterpret someone's code.
This subject can be deleted, it's going nowhere.

[José Roca]

Use:

LOCAL hr AS LONG
LOCAL pEnum AS IEnumVARIANT
LOCAL IID_IEnumVARIANT AS GUID
IID_IEnumVARIANT = $IID_IEnumVARIANT
hr = oNodeList.QueryInterface(IID_IEnumVARIANT, BYVAL VARPTR(pEnum))

[Edwin Knoppert]

Oops, though that wasn't possible.
When i took a closer look i was thinking you did this on the resulting interface.

Could this mean i don't need the Invoke(-4) stuff for any late bound Dispatch interface?

[Edwin Knoppert]

This works:

        If oDisp.Invoke( -4, IID_NULL, 0, 1 Or 2, udispparams, vResult, ByVal VarPtr( pExcepInfo ), puArgErr ) = 0 Then
            oEnum = vResult: vResult = Empty
        End If

This not:

        Local pUnk As Dword Ptr
        If oDisp.QueryInterface($IID_IEnumVARIANT, ByVal VarPtr(pUnk)) = 0 Then
        End If

pUnk remains 0

[José Roca]

For some reason, the built-in QueryInterface method does not work if you pass a constant. Use a variable as I did in my previous post:

        Local pUnk As Dword Ptr
        Local IID_IEnumVARIANT As GUID
        IID_IEnumVARIANT = $IID_IEnumVARIANT
        If oDisp.QueryInterface(IID_IEnumVARIANT, ByVal VarPtr(pUnk)) = 0 Then
        End If

[Edwin Knoppert]

Cool!

Much better than the invoke..

[José Roca]

But be aware that these built-in methods are undocumented...

[Edwin Knoppert]

That is a compiler issue and solvable.
For me it's more important i can use this on any interface (unknown/dispatch) which supports the enumeration.

And -4 is a 'fixed' member also and i could use this but i like this better.

I also believe this will help me with non-dual interfaces.

[Edwin Knoppert]

Oh btw, i used call dword with vtable offsets, forgot to memtion.
I just rewrote it.

[Edwin Knoppert]

is it possible to implement this enumerator interface into PB classes?
Maybe simply adding it icw it's guid?
I don't have much influence on the QueryInterface is it?

[José Roca]

The classic way is to add the _NewEnum method/property to your collection class and, in that method, return a pointer to your implementation of the IEnumVARIANT class. Calling QueryInterface for IEnumVARIANT won't work if the enumerator isn't implemented in the same class.

[José Roca]

Could this mean i don't need the Invoke(-4) stuff for any late bound Dispatch interface?

Calling the _NewEnum method (dispID -4) is the safer way, and the only that will work if you write a component to be used by languages such VB that use the FOR EACH construct.

[Edwin Knoppert]

I'll make this the 2nd option then.
Thanks,