kulwant1977

 Profile Answers by kulwant1977 Questions by kulwant1977

• Sep 20th, 2005

 

RTTI as known Runtime Type Identification.
If you want to cast the object of one class as the object of another class so u require to know the type of the object at the runtime and u may want to cofirm is tht object of the same class you want to change we use the typeid operator to check what is the objects type and then use dynamic cast to cast the object.

apiplani

 Profile Answers by apiplani 

• Jan 2nd, 2006

 

Does this mean that RTTI is the term used for resolution of the function at the run time. As far as I understand in case of virutal functions as well the compiler resolves at the run time the exact function to be used. Will this resolution be also termed as RTTI??????

A

• Jan 28th, 2006

 

In case of Virtual function we are responsible for deciding the function at run time. Its our logic that reflects and no one does any thing.

Where as in case of RTTI TYPE is found of object. We dont do any thing for that. We simply use that.

mohit12379

 Profile Answers by mohit12379 Questions by mohit12379

• Apr 20th, 2006

 

Run-time type information (RTTI) is a mechanism that allows the type of an object to be determined during program execution. RTTI was added to the C++ language because many vendors of class libraries were implementing this functionality themselves. This caused incompatibilities between libraries. Thus, it became obvious that support for run-time type information was needed at the language level.

There are three main C++ language elements to run-time type information:

1)The dynamic_cast operator. :- Used for conversion of polymorphic types.
 
  class B { ... };
  class C : public B { ... };
  class D : public C { ... };
 
  void f(D* pd)
  {
     C* pc = dynamic_cast<C*>(pd);// ok: C is a direct base class
                                  // pc points to C subobject of pd
 
     B* pb = dynamic_cast<B*>(pd);// ok: B is an indirect base class
                                  // pb points to B subobject of pd
     ...
  }
---------------------------------------------------------------------------
2)The typeid operator :- Used for identifying the exact type of an object.
                       
3)The type_info class :- Used to hold the type information returned by the typeid operator.
                         The type_info class describes type information generated within the
                         program by the compiler.
 
NOTE:-   TRY THIS EXAMPLE IS COMPILE AND LINK USING MSVC++ 6.0 CL.EXE Compiler and Linker PLS CHECK SAME typid available in UNIX based C++;
 **************************************************************************************                       
 #include "stdio.h"
 #include <typeinfo.h>
 
 class A
 {
 public:
 };
 
 class B:public A
 {
 public:
 };
 
 int main(int argc, char* argv[])
 {
    int   iVal = int();
    float fVal = float();
    char  cVal = char();
    A a,a1;
    B b;
 

    const type_info& t_iVal = typeid(iVal);   // Holds Simple int DataType Info
    const type_info& t_iValRef = typeid(&iVal); // Holds pointer type_info

    printf("\n Type Info of  iVal = %s\n",t_iVal.name());
    printf("\n Type Info of &iVal = %s\n",t_iValRef.name());
 
    printf("\n Type Info of fVal = %s\n",typeid(fVal).name());
    printf("\n Type Info of &fVal = %s\n",typeid(&fVal).name());
 
    printf("\n Type Info of cVal = %s\n",typeid(cVal).name());
    printf("\n Type Info of &cVal = %s\n\n",typeid(&cVal).name());
 
    printf("\n Type Info of a = %s\n",typeid(a).name());
    printf("\n Type Info of b = %s\n\n",typeid(b).name());
 
    if(typeid(a) == typeid(a1))
    {
     printf("\n BOTH INSTANCES a AND a1 BELONGS TO SAME CLASS \n\n");
    }
 
    return 0;
}
****************************************************************************
                         
 PLS ANY  DOUBT WRITE ME AT mohit.gonduley@gmail.com