Understanding of C + + polymorphism

 

1. Say in front:

The project is largely resolved and now frees up time to optimize the project and learn new knowledge.

2.c++ polymorphism

1. Description: (polymorphic) polymorphism

For C + + polymorphism, this is a very flexible technology, the use of very smart, difficult; Simply put: polymorphism is the appropriate use of interface functions, through an interface to use a variety of methods, (equivalent to the superior said a command, a,b,c,d and other people are reacting, a command, multiple responses;

2. How to achieve polymorphism

1. Using virtual functions and pointers for polymorphism

A virtual function is used to define a method to be implemented, and a pointer to a base class that points to a virtual function method of a different subclass

2. The advantage of polymorphism is to implement interface reuse

3. Virtual function:

1. Virtual function uses the keyword virtual modification, virtual function allows subclasses to redefine the member function;

2. Rewrite (the function name is the same, but the content is inconsistent)//also known as overwrite (override)

3. Overloading (the function name is the same, but the parameter table column is inconsistent)

4. Polymorphism is typically done by rewriting virtual functions, then pointing to different sub-objects with a base-class pointer, calling different virtual functions

4. Code implementation

[CPP]View PlainCopy

2. #include <iostream>
4. #include <stdlib.h>
6. #include <string>
8. Using namespace std;
10. Class IShape
12. {
14. Public
16. //Polymorphism implementation requires virtual method
18. virtual double get_area () = 0;
20. virtual String get_name () = 0;
22. };
24. Defining Class 1 Ccircle
26. Class Ccircle: Publicishape
28. {
30. //Declaration need to bring the virtual keyword to show polymorphism
32. Public
34. Ccircle (double radius) {This->c_radius = radius;}
36. Ccircle () {}
38. virtual double Get_area ();
40. virtual string get_name ();
42. Private
44. double C_radius; //Define the radius of the circle
48. };
50. Defining methods
54. Double Ccircle::get_area ()
56. {
58. return 3.14*c_radius*c_radius;
60. }
62. String Ccircle::get_name ()
64. {
66. return "Ccircle";
68. }
70. Class CRect: Publicishape
72. {
74. Public
76. CRect (double length, double width) { this->m_length = length, this->m_width = width;}
78. CRect () {};
80. virtual double Get_area ();
82. virtual string get_name ();
84. Private
86. double m_length;
88. double m_width;
90. };
92. Double Crect::get_area ()
94. {
96. return m_length*m_width;
98. }
100. String Crect::get_name ()
102. {
104. return "Rectangle";
106. }
110. Pointing to different classes with pointers and using different methods
112. #include "Text.h"
118. void Main ()
120. {
122. <span style="WHITE-SPACE:PRE;" > </span>ishape *point = NULL; //Build pointer
124. <span style="WHITE-SPACE:PRE;"  > </span>point = new Ccircle (10);
126. <span style="WHITE-SPACE:PRE;" > </span>//round type
132. <span style="WHITE-SPACE:PRE;"  > </span>cout << point->get_name () << "area is:" << point->get_area () << Endl;
134. <span style="WHITE-SPACE:PRE;"  > </span>Delete point;
136. <span style="WHITE-SPACE:PRE;" > </span>//Rectangle class
138. <span style="WHITE-SPACE:PRE;"  > </span>point = new CRect (10, 20);
140. <span style="WHITE-SPACE:PRE;"  > </span>cout << point->get_name () << "area is:" << point->get_area () << Endl;
142. <span style="WHITE-SPACE:PRE;"  > </span>Delete point;
144. <span style="WHITE-SPACE:PRE;"  > </span>system ("pause");
146. }
164. <span style="WHITE-SPACE:PRE;" > </span>
174. <span style="WHITE-SPACE:PRE;" > </span>
180. <span style="WHITE-SPACE:PRE;" > </span>
182. <span style="WHITE-SPACE:PRE;" > </span>

Understanding of C + + polymorphism