对象切片与虚函数机制

C++语言: Codee#25744

01 /*
02    对象切片
03    此处为传值 注意与传地址相比较
04    */
05 #include <iostream>
06 #include <string>
07 using namespace std;
08
09 class Pet
10 {
11     string pname;
12 public:
13     Pet(const string& name)
14         : pname(name)
15     {}
16     virtual string name() const
17     {
18         return pname;
19     }
20     virtual string description() const
21     {
22         return "This is " + pname;
23     }
24 };
25
26 class Dog: public Pet
27 {
28     string favoriteActivity;
29 public:
30     Dog(const string& name, const string& activity)
31         : Pet(name), favoriteActivity(activity)
32     {}
33     string description() const
34     {
35         return Pet::name() + " likes to " +
36                favoriteActivity;
37     }
38 };
39
40 void describe(Pet p)
41 {
42     cout << p.description() << endl;
43 }
44
45 int main()
46 {
47     Pet p("Alfred");
48     Dog d("Fluffy", "sleep");
49     describe(p);
50     describe(d);
51
52     return 0;
53 }
54 /*
55 This is Alfred
56 This is Fluffy
57
58 Process returned 0 (0x0)   execution time : 0.070 s
59 Press any key to continue.
60
61 */

C++语言: Codee#25745

01 /*
02    地址传递
03    启用虚函数机制
04    */
05 #include <iostream>
06 #include <string>
07 using namespace std;
08
09 class Pet
10 {
11     string pname;
12 public:
13     Pet(const string& name)
14         : pname(name)
15     {}
16     virtual string name() const
17     {
18         return pname;
19     }
20     virtual string description() const
21     {
22         return "This is " + pname;
23     }
24 };
25
26 class Dog: public Pet
27 {
28     string favoriteActivity;
29 public:
30     Dog(const string& name, const string& activity)
31         : Pet(name), favoriteActivity(activity)
32     {}
33     string description() const
34     {
35         return Pet::name() + " likes to " +
36                favoriteActivity;
37     }
38 };
39
40 void describe(Pet* p)
41 {
42     cout << p->description() << endl;
43 }
44
45 int main()
46 {
47     Pet* p = new Pet("Alfred");
48     Dog* d = new Dog("Fluffy", "sleep");
49     describe(p);
50     describe(d);
51
52     return 0;
53 }
54 /*
55 This is Alfred
56 Fluffy likes to sleep
57
58 Process returned 0 (0x0)   execution time : 0.059 s
59 Press any key to continue.
60
61
62
63 */