C Friend-Friend

C Friend-Friend

Friend is used to break the limit of protected or private protection, the first thing to do is to be declared in the class of the visitor is a friend function or friend class. The code is as follows

2. #include <iostream>
   
4. using namespace Std;
   
8. Class Square{
   
10. Private:
    
12. int side;
    
14. Public:
    
16. Square(int a): Side(a){}
    
18. Friend class Rectangle ; //declare the Class is friend
    
24. };
    
28. Class Rectangle {
    
30. Private:
    
32. int width, height;
    
34. Public:
    
36.                 rectangle< Span style= "color: #0000cc;" > (int aint B) :width (A) ,height (B{
    
38. void Set_values (int a, int b){
    
40. Width = a;
    
42. Height = b;
    
44. }
    
46. int Girth();
    
48. Friend int area (Rectangle &); //declare the friend function here
    
50. int get_width(){return width;}
    
52. int get_height(){return height;}
    
54. void Conver_from_square(square &s){
    
56. Width = Height = s. Side; //access so easily
    
58. }
    
60. };
    
64. //implement The function here , Access easily , too
    
66. int area (Rectangle &r){return (r. Width * r. Height); }
    
68. int r_area (Rectangle &r{return R.get_width (* R.get_height (;
    
70. int Rectangle:: Girth(){return width + width + height + height; }
    
74. int main () {
    
76. Test_sizeof:
    
78. cout << "Sizeof:square" << sizeof(Square)
    
80. << ", \trectangle" << sizeof(Rectangle) << "\ n" ;
    
82. Test_access:
    
84. Rectangle R(2, 3);
    
86.         cout < < << area (R<< Span style= "color: #0000cc;" >< <.girth () << endl
88. cout << "Onather Way:area" << R_area(R) << Endl;
    
92. Rectangle R1(2, 3);
    
94. Square s(5);
    
96. R1. Conver_from_square(S);
    
98. cout << "Rectangle convering from Square, girth is" << R1. Girth() < ; < Endl;
    
100. return 0;
     
102. }

Results

1. Sizeof:square 4, Rectangle 8
3. Area:6 girth:10
4. Onather Way:area 6
5. Rectangle convering from Square, girth is 20

Look at the function

• Area
• R_area
• Girth

if it is not a friend function or class, the access case, such as the R_area () function, allows the friend function to access the member directly. But there is a difference between the member function and the function girth ()

Look at size, the friend or friend function does not increase the size of the class, just declare it.

C Friend-Friend