enum可以做索引

enum可以做索引，配上虚函数，或者函数指针，可以实现上层的统一封装和快速索引。

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MoTbl.cpp
#include <stdio.h>
#include <stdlib.h>
enum {
eA=0,
eB,
eC,
eD,
eMax
};
class Bs{
public:
virtual void say(){ printf("Bs\n"); }
};
class A: public Bs{
int aa[1];
public:
void say(){printf("A\n");}
void call(){printf("A::call\n");}
};
class B: public Bs{
int aa[3];
public:
void say(){printf("B\n");}
void sing(){printf("B::sing\n");}
};
class C: public Bs{
int aa[10];
public:
void say(){printf("C\n");}
};
class D: public Bs{
int aa[100];
public:
void say(){printf("D\n");}
};
class MoTbl{
public:
union{
struct{
A *a;
B *b;
C *c;
D *d;
}t;
void *tv[eMax];
};
};
int
main ( int argc, char *argv[] )
{
int i = 0;
MoTbl mt;
A a;
B b;
C c;
D d;
printf("A:%d\n",sizeof(MoTbl));
for(i=0; i<eMax; i++)
printf("%p\n",mt.tv[i]);
printf("--------------\n");
mt.tv[eA] = &a;
mt.tv[eB] = &b;
mt.tv[eC] = &c;
mt.tv[eD] = &d;
for(i=0; i<eMax; i++)
printf("%p\n",mt.tv[i]);
printf("--------------\n");
mt.t.a->say();
printf("--------------\n");
for(i=0; i<eMax; i++){
switch(i){enum 做索引 2012-10-11 18:17:14

分类： C/C++

enum可以做索引，配上虚函数，或者函数指针，可以实现上层的统一封装和快速索引。
点击(此处)折叠或打开
1. MoTbl.cpp
2. #include <stdio.h>
3. #include <stdlib.h>
4. enum {
5. eA=0,
6. eB,
7. eC,
8. eD,
9. eMax
10. };
11. class Bs{
12. public:
13. virtual void say(){ printf("Bs\n"); }
14. };
15. class A: public Bs{
16. int aa[1];
17. public:
18. void say(){printf("A\n");}
19. void call(){printf("A::call\n");}
20. };
21. class B: public Bs{
22. int aa[3];
23. public:
24. void say(){printf("B\n");}
25. void sing(){printf("B::sing\n");}
26. };
27. class C: public Bs{
28. int aa[10];
29. public:
30. void say(){printf("C\n");}
31. };
32. class D: public Bs{
33. int aa[100];
34. public:
35. void say(){printf("D\n");}
36. };
37. class MoTbl{
38. public:
39. union{
40. struct{
41. A *a;
42. B *b;
43. C *c;
44. D *d;
45. }t;
46. void *tv[eMax];
47. };
48. };
49. int
50. main ( int argc, char *argv[] )
51. {
52. int i = 0;
53. MoTbl mt;
54. A a;
55. B b;
56. C c;
57. D d;
58. printf("A:%d\n",sizeof(MoTbl));
59. for(i=0; i<eMax; i++)
60. printf("%p\n",mt.tv[i]);
61. printf("--------------\n");
62. mt.tv[eA] = &a;
63. mt.tv[eB] = &b;
64. mt.tv[eC] = &c;
65. mt.tv[eD] = &d;
66. for(i=0; i<eMax; i++)
67. printf("%p\n",mt.tv[i]);
68. printf("--------------\n");
69. mt.t.a->say();
70. printf("--------------\n");
71. for(i=0; i<eMax; i++){
72. switch(i){
73. case eA: mt.t.a->say(); break;
74. case eB: mt.t.b->say(); break;
75. case eC: mt.t.c->say(); break;
76. case eD: mt.t.d->say(); break;
77. }
78. }
79. printf("--------------\n");
80. for(i=0; i<eMax; i++)
81. ((Bs *)mt.tv[i])->say();
82. printf("--------------\n");
83. for(i=0; i<eMax; i++){
84. switch(i){
85. case eA: mt.t.a->call(); break;
86. case eB: mt.t.b->sing(); break;
87. }
88. }
89. printf("--------------\n");
90. }
输出
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1. A:16
2. 0xb7726ff4
3. 0xb77238e4
4. (nil)
5. 0xb7615ff4
6. --------------
7. 0xbff0cd98
8. 0xbff0cd88
9. 0xbff0cd5c
10. 0xbff0cbc8
11. --------------
12. A
13. --------------
14. A
15. B
16. C
17. D
18. --------------
19. A
20. B
21. C
22. D
23. --------------
24. A::call
25. B::sing
26. --------------
case eA: mt.t.a->say(); break;
case eB: mt.t.b->say(); break;
case eC: mt.t.c->say(); break;
case eD: mt.t.d->say(); break;
}
}
printf("--------------\n");
for(i=0; i<eMax; i++)
((Bs *)mt.tv[i])->say();
printf("--------------\n");
for(i=0; i<eMax; i++){
switch(i){
case eA: mt.t.a->call(); break;
case eB: mt.t.b->sing(); break;
}
}
printf("--------------\n");
}

输出

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A:16
0xb7726ff4
0xb77238e4
(nil)
0xb7615ff4
--------------
0xbff0cd98
0xbff0cd88
0xbff0cd5c
0xbff0cbc8
--------------
A
--------------
A
B
C
D
--------------
A
B
C
D
--------------
A::call
B::sing
--------------

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enum可以做索引

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