Friend Functions

Friend functions are declared outside the class body. They have access to all private and protected members of the class.

Syntax:

class ClassName { // class body // marking functions as friend friend funcType funcName(args); }; // defining the function funcType funcName(args) { // function body }

Example:

#include <iostream> using namespace std; class Rectangle { private: double width; double height; public: // friend function with no body friend double area(Rectangle rect); Rectangle(double widthValue, double heightValue) { width = widthValue; height = heightValue; } }; // defining function's body double area(Rectangle rect) { return rect.width * rect.height; } void main() { Rectangle rect(3, 2); cout << "Area = " << area(rect); }

Output:

Area = 6

Explanation:

• At line 13 a function is marked as "friend". It has no body inside the class.
• At lines 23 - 26 the friend function is declared. The body of a friend function is declared outside the class.
• At line 32 the friend function is called.