Is there any way I can call child method from parent class? - oop

Question

I am building a game for cocos2d-x and want to call child class method from parent class.
class Parent {
*//do something
//How can i call method from subchild class here?*
}
class Child : Parent {
*//do something*
}
class SubChild : Child {
void functionToBeCalledFromParent();
}

Answer 1

I am building a game for cocos2d-x and want to call child class method from parent class
You can 1) declare the function In parent and define it in the child or 2) define it in parent and override it (re-define it) in child.

Answer 2

By using CRTP, your example
class Parent {
void callSubclassFunction() {
//How can i call method from subchild class here?
}
}
class Child : Parent {
}
class SubChild : Child {
void functionToBeCalledFromParent();
}
would turn into
#include <iostream>
template <typename TSubclass>
class Parent {
public:
void callSubclassFunction() {
static_cast<TSubclass*>(this)->functionToBeCalledFromParent();
}
};
template <typename TSubclass>
class Child : public Parent<TSubclass> {
};
class SubChild : public Child<SubChild> {
public:
void functionToBeCalledFromParent() {
std::cout << "SubChild!" << std::endl;
}
};
int main()
{
SubChild child;
child.callSubclassFunction();
}
Runnable at Coliru
Passing SubChild as template parameter to Child<> works because the typename is valid as soon it's declared, which it is just in front of the inheritance list divider :.
Using static_cast to "downcast" in Parent is completely benign here. If the subclass doesn't define the function called in Parent, the compilation will just fail.
This technique is called static or compile-time polymorphism and it's what the ATL and WTL are built upon. The oppsosite and perhaps more conventional method would be dynamic or runtime polymorphism and it's what you get with virtual functions.