Calling function of Exe project in referenced aticvex project in vb6
I have one AtiveX project in VB6 (Lets call it A )
i have another Exe project in VB6 (Lets call it B )
Project A is referenced in Project B
but now i have a requirement that i want to call function of B inside A
is there a way Can we do it in VB6?
if yes what do i need to search.Already tried searching on Google but not sure i could explain what to search
As i didn't work much on VB6 so i am kind a stuck here what to do
First off let me say that when you run into this problem it is often a sign that the code organization could be improved. Perhaps some modules in A actually should be in B, or they could be broken down in a more modular way that would resolve the problem. I would first encourage you to think about the problem this way.
That said, there are technical ways of doing what you want, I've suggested some examples below.
One approach to this is to utilize an interface. The interface would be provided by A.dll and the class used to implement it is provided by B.exe.
This is rough pseudocode just to sketch out the concept.
Within project A:
Create a class to act as an interface (called ISample). Within ISample have at least one sub or function defined, so you would have ISample.SomeProcedure.
Elsewhere in project A, you need some property or procedure SomeClassInA.RunSampleFunction which will accept an object of type ISample and then call SomeFunction.
Within project B:
Create another class SampleImplementation which Implements the ISample interface. This means it will have an actual concrete implementation of SomeFunction.
From B, create a new object of type SampleImplementation and then pass it to the code in A:
Dim impl As SampleImplementation
Dim objectFromA As SomeClassInA
Set impl = New SampleImplementation
Set objectFromA As New SomeClassInA
' Pass the object from B to A, where A can call its methods:
objectFromA.SomeProcedure impl
This avoids circular references and is a generally object-oriented pattern which I've used before. I will note however that the interface concept in VB6 has some annoyances that you'll have to live with, but for something like this it can be a good tool.
A different approach would be to have a class in A which exposes an event. You can then declare an object from that class in B using WithEvents and attach an event handler to the class. The event handler is just a procedure which exists in B, but now can be called by A.
Events in VB6 also have some limitations (specifically that the WithEvents object has to be within global scope IIRC) but you can usually live with / work around those problems as well.
The interface approach may be more general and a more powerful way to share information between A and B, but the event approach could be quicker to get working. Depends a lot on the specifics of what you need to accomplish.