RTTI的一个例子

深入浅出MFC的一个例子:

2. //RTTI.CPP---built by cl -GR  rtti.cpp <enter>
3. #include <typeinfo.h>
4. #include <iostream>
5. #include <string.h>
6. using namespace std;
8. class graphicImage
9. {
10.     protected:
11.         char name[80];
12.         public:
13.             graphicImage()
14.             {
15.                 strcpy(name,"graphicImage");
16.             }
17.             
18.             virtual void display()
19.             {
20.                 cout<<"Display a generic image."<<endl;
21.             }
22.             
23.             char * getName()
24.             {
25.                 return name;
26.             }
27. };
28. //================================================
29. class GIFimage : public graphicImage
30. {
31.     public:
32.         GIFimage()
33.         {
34.             strcpy(name,"GIFimage");
35.         }
37.     void display()
38.     {
39.         cout<<"Display a GIF file."<<endl;
40.     }
41. };
42. /////////////////////////////////////////////
43. class PICTimage: public graphicImage
44. {
45.     public:
46.         PICTimage()
47.         {
48.             strcpy(name,"PICTimage");
49.         }
50.         void display()
51.         {
52.             cout<<"Display a PICT file."<<endl;
53.         }
54. };
55. ///////////////////////////////////////
56. void processFile(graphicImage *type)
57. {
58.     if(typeid(GIFimage)==typeid(*type) )
59.     {
60.       ((GIFimage*)type)->display();
61.     }   
62.     else if(typeid(PICTimage)==typeid(*type))
63.     {
64.         ((PICTimage*)type)->display();
65.     }
66.     else
67.     cout<<"Unknow type!"<<(typeid(*type)).name()<<endl; 
68. }
69. ////////////////////////////////
70. void main()
71. {
72.     graphicImage *gImage=new GIFimage();
73.     graphicImage *pImage=new PICTimage();
74.     processFile(gImage);
75.     processFile(pImage);
76. }

 

若在DOS 下,一切正常.

若在VC6.0 IDE环境下编译,出错.

f:/rtti.cpp(57) : warning C4541: 'typeid' used on polymorphic type 'class graphicImage' with /GR-; unpredictable behavior may result
查MS

Compiler Warning (level 1) C4541

'identifier' used on polymorphic type 'type' with /GR-; unpredictable behavior may result

You did not enable run-time type information and tried to use a feature that requires run-time type information support. Recompile with the /GR switch.

For more information, see the Enable Run-Time Type Information (/GR) compiler option.

 

 

/GR   (Enable Run-Time Type Information)

The Enable Run-Time Type Information option (/GR) causes the compiler to add code to check object types at run time. When this option is specified, the compiler defines the _CPPRTTI preprocessor macro. The option is cleared (/GR–) by default.

To find this option in the development environment, click Settings on the Project menu. Then click the C/C++ tab, and click C++ Language in the Category box.

For more information on run-time type checking, see Run-Time Type Information in the C++ Language Reference.