Multiple Inheritance from two derived classes

Question

I have an abstract base class which acts as an interface.

I have two \"sets\" of derived classes, which implement half of the abstract class. ( one \"set\" defines t

Answer 1

It can be done, although it gives most the shivers.

You need to use "virtual inheritance", the syntax for which is something like

class AbsInit: public virtual AbsBase {...};
class AbsWork: public virtual AbsBase {...};
class NotAbsTotal: public AbsInit, public AbsWork {...};

Then you have to specify which function you want to use:

NotAbsTotal::work()
{
    AbsInit::work_impl();
}

(UPDATED with correct syntax)

Answer 2

You have to start thinking in the terms of what you are trying to model here.

Public inheritance should only ever be used to model an "isa" relationship, e.g. a dog is a animal, a square is a shape, etc.

Have a look at Scott Meyer's book Effective C++ for an excellent essay on what the various aspects of OO design should only ever be interpreted as.

Edit: I forgot to say that while the answers so far provided are technically correct I don't think any of them address the issues of what you are trying to model and that is the crux of your problem!

HTH

cheers,

Rob

Answer 3

It looks like you want to do virtual inheritance. Whether that turns out to actually be a good idea is another question, but here's how you do it:

class AbsBase {...};
class AbsInit: public virtual AbsBase {...};
class AbsWork: public virtual AbsBase {...};
class NotAbsTotal: public AbsInit, public AbsWork {...};

Basically, the default, non-virtual multiple inheritance will include a copy of each base class in the derived class, and includes all their methods. This is why you have two copies of AbsBase -- and the reason your method use is ambiguous is both sets of methods are loaded, so C++ has no way to know which copy to access!

Virtual inheritance condenses all references to a virtual base class into one datastructure. This should make the methods from the base class unambiguous again. However, note: if there is additional data in the two intermediate classes, there may be some small additional runtime overhead, to enable the code to find the shared virtual base class.

Answer 4

You need to to declare the inheritance as virtual:

struct AbsBase {
          virtual void init() = 0;
          virtual void work() = 0;
};

struct AbsInit : virtual public AbsBase {
          void init() {  }
};

struct AbsWork : virtual public AbsBase {
          void work() { }
};

struct NotAbsTotal : virtual public AbsInit, virtual public AbsWork {
};

void f(NotAbsTotal *p)
{
        p->init();
}

NotAbsTotal x;

Answer 5

I found a good and simple example at the below link. The article explains with an example program for calculating the area and perimeter of a rectangle. You can check it..cheers

Multilevel Inheritance is an inheritance hierarchy wherein one derived class inherits from multiple Base Classes. Read more..

http://www.mobihackman.in/2013/09/multiple-inheritance-example.html