C++ Class

>Abstraction

>Encapsulation /Access Modifiers

>Inheritance

1. #include <iostream>
2. using namespace std;
3. 
   
4. class vehicle
5. {
6. public:
7.     vehicle()
8.     {
9.         cout<<"this is a constructor of vehicle"<<endl;
10.     }
11.     ~vehicle()
12.     {
13.         cout<<"this is a deconstructor of vehicle"<<endl;
14.     }
15. };
16. 
    
17. class fourwheeler
18. {
19. public:
20.     fourwheeler()
21.     {
22.         cout<<"this is the constructor of fourwheeler"<<endl;
23.     }
24.     fourwheeler(string x)
25.     {
26.         cout<<"This is another constructor which has "<<x<<" with it"<<endl;
27.     }
28.     ~fourwheeler()
29.     {
30.         cout<<"this is deconstructor of fourwheeler"<<endl;
31.     }
32. };
33. 
    
34. //Single Inheritance
35. 
    
36. class Car: public vehicle
37. {
38.     public:
39.     Car()
40.     {
41.         cout<<"this is a derrived child class from vehicle 's constructor"<<endl;
42.     }
43.     ~Car()
44.     {
45.         cout<<"this is a deconstructor of Car which is derrived from vehicle"<<endl;
46.     }
47. };
48. 
    
49. //multiple inheritance
50. 
    
51. class nuhash: public vehicle,public fourwheeler
52. {
53.     public:
54.     nuhash()
55.     {
56.         cout<<"this is  a constructor of nuhash"<<endl;
57.     }
58.     nuhash(string x)
59.     {
60.         cout<<"this is a constructor of nuhash with "<<x<<"with it"<<endl;
61.     }
62.     ~nuhash()
63.     {
64.         cout<<"this is a deconstructor of nuhash"<<endl;
65.     }
66. };
67. 
    
68. //multilevel inheritance
69. 
    
70. class nuhan:public nuhash
71. {
72. public:
73.     nuhan()
74.     {
75.         cout<<"constructor of nuhan"<<endl;
76.     }
77.     ~nuhan()
78.     {
79.         cout<<"de constructor of nuhan"<<endl;
80.     }
81. };
82. 
    
83. //multilevel inheritance//derived from nuhan and nuhan is derived from nuhash when nuhash is derived from vehicle and four wheeler
84. 
    
85. class ira:public nuhan
86. {
87. public:
88.     ira()
89.     {
90.         cout<<"constructor of ira"<<endl;
91.     }
92.     ~ira()
93.     {
94.         cout<<"de constructor of ira"<<endl;
95.     }
96. };
97. 
    
98. // car and nuhash is example of tree inheritance + hybrid as they are both derrived from vehicle
99. 
    
100. int main()
101. {
102.     ira obj;
103.     return 0;
104. }

• //Details here!

Frined Class and Friend Function

• Accessing Class's object by another class/class's fucntion/user define functions

1. #include <iostream>
2. using namespace std;
3. 
   
4. 
   
5. //class -> class friend
6. class nuhash
7. {
8. private:
9.     int password;
10. public:
11.     nuhash()
12.     {
13.         password=12131313;
14.     }
15.     friend class Noman;
16. };
17. 
    
18. class Noman
19. {
20. private:
21.     int gf_count;
22. public:
23.     Noman()
24.     {
25.         gf_count=1;
26.     }
27.     void showNoman(nuhash &x)
28.     {
29.         cout<<"nuhash's password "<<x.password<<endl;
30.     }
31.     void gf()
32.     {
33.         cout<<gf_count<<endl;
34.     }
35. };
36. 
    
37. //class -> function friend
38. class CF;
39. 
    
40. class UVA
41. {
42. private:
43.     int submission;
44. public:
45.     void show(CF& x);
46. } ;
47. 
    
48. class CF
49. {
50. private:
51.     int user;
52. public:
53.     CF()
54.     {
55.         user=100;
56.     }
57.     friend void UVA::show(CF& x);
58.     //class->normal function
59.     friend int pow(CF &x);
60. };
61. 
    
62. void UVA::show(CF &x)
63. {
64.     cout<<x.user<<endl;
65. }
66. 
    
67. int pow(CF& x)
68. {
69.     cout<<x.user*23<<endl;
70. }
71. 
    
72. int main()
73. {
74.     CF x;
75.     UVA y;
76.     y.show(x);
77.     pow(x);
78. }

Note:

• In C++ friend function or class is not inherited
• Like CR's friend wont be his child's friend and his child's friend will not be his friend
• Derived class wont have the  friend function the parent had
• To use the friend function in derived class we have to declare it in derived function again