Re: Question about inheritance
maverik <maverik.mail@gmail.com> wrote:
Hi all.
There is one question about inheritance:
I have base class, lets say it is IInterface:
class IInterface {
virtual void foo();
};
and derived class:
class Implementation : public IInterface {
void foo() { do_something(); }
// Many more functions here
void func1();
void func2();
...
void funcN();
};
I want to create class that allows clients to call func1(), ... , funcN
() function, but doesn't allow to call functions from base class (in
our case foo() ). How can I do this?
The only way is to remove the public inheritance.
One way that will get close:
class IInterface {
public:
virtual void foo();
};
class Implementation : public IInterface {
private:
void foo();
public:
void func1(); // etc.
};
But the caller will still be able to call 'foo()' if he wants by simply
casting the Implementation object or passing it to a context that uses
an IInterface.
I try the following:
class IInterface {
public:
virtual void foo() = 0;
};
class Implementation: public IInterface {
public:
void foo() { std::cout << "Implementation::foo();\n"; };
void bar() { std::cout << "Implementation::bar();\n"; };
};
template<class T>
class MyClass : private IInterface, public T {
public:
void tee() {}
};
MyClass<Implementation> c;
but VC 9.0 says me:
error C2259: 'MyClass<T>' : cannot instantiate abstract class
Unfortunately can't test this on gcc.
Of course, I can write MyClass as a copy of Implementation class, but
with private or protected inheritance from IInterface, but
Implementation in real is a big class (and not only one, there is
bunch of such classes).
The solution here is to not make "real big" classes.