Question

I will describe the problem as simple as i can.

alright, here goes the problem;

Lets suppose we have a com component class with 3 of constructors where a constructor takes at least two of parameters. As we already know we instantiate the components via QueryInterface rather calling the classes’ constructors therefore it seems it is not possible for a com client to set the constructor’s parameters.

alright, here goes the question;

What is the best practical approach to allow a com client to instantiate a com component which requires at least two of parameters to be initialized?

Answer 1

Instead of directly returning object instances, your QueryInterface call can return factories. For example, instead of:

// implements IMyClass1 interface
return new MyClass1();

You would do:

// pointer to member that implements IMyClassFactory interface
return &m_myClassFactory;
// this could also be a static class instead of an object instance

The IMyClassFactory interface would have a create method that takes in the constructor arguments and returns the ultimate MyClass1 instance.