Trisha Shetty (Editor)

Friend class

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A friend class in C++ can access the private and protected members of the class in which it is declared as a friend.

Contents

Rationale

Friendship may allow a class to be better encapsulated by granting per-class access to parts of its API that would otherwise have to be public. This increased encapsulation comes at the cost of tighter coupling due to interdependency between the classes.

Properties

  • Friendships are not symmetric – if class A is a friend of class B, class B is not automatically a friend of class A.
  • Friendships are not transitive – if class A is a friend of class B, and class B is a friend of class C, class A is not automatically a friend of class C.
  • Friendships are not inherited – if class Base is a friend of class X, subclass Derived is not automatically a friend of class X; and if class X is a friend of class Base, class X is not automatically a friend of subclass Derived.

    • References

    Friend class Wikipedia
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