c++ friend class

A friend class in C++ is a class that has access to the private and protected members of another class. To define a friend class, follow these steps:

1. Declare the friend class: Start by declaring the friend class within the class that it wants to access. This is done by including a friend declaration inside the class definition. For example:

class MyClass {
    friend class FriendClass;
};

1. Define the friend class: Next, define the friend class outside of the class that it wants to access. This is done by writing the class definition as usual. For example:

class FriendClass {
    // Class definition
};

1. Access private and protected members: Once the friend class is defined, it can access the private and protected members of the class that declared it as a friend. This means that the friend class can directly access and modify the private and protected members of the declaring class. For example:

class MyClass {
private:
    int privateVar;

protected:
    int protectedVar;

    friend class FriendClass;
};

class FriendClass {
public:
    void accessPrivateProtected(MyClass& obj) {
        obj.privateVar = 10;         // Access private member
        obj.protectedVar = 20;       // Access protected member
    }
};

In the above example, the FriendClass is declared as a friend of MyClass. This allows FriendClass to access the private member privateVar and the protected member protectedVar of MyClass. The accessPrivateProtected function demonstrates how the friend class can access and modify these members.

Remember that the friend relationship is not reciprocal - just because FriendClass can access the private and protected members of MyClass, it doesn't mean that MyClass can access the private and protected members of FriendClass.

That's it! You have successfully defined and used a friend class in C++. I hope this explanation helps!