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  4. typeid operator

typeid operator

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  • J jmkhael

    just tried this and it works CString temp; CString temp1; const type_info& t = typeid(temp); AfxMessageBox (t.name ()); // It gave class CString if(typeid(temp1) == typeid(CString)) AfxMessageBox ("Matched"); // It said matched Check this too: class Base { ... }; class Derived : public Base { ... }; void f() { Derived* pd = new Derived; Base* pb = pd; ... const type_info& t = typeid(pb); // t holds pointer type_info const type_info& t1 = typeid(*pb); // t1 holds Derived info ... } (This is your prob, you should dereference the pointer) What does yours do? Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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    kfaday
    wrote on last edited by
    #7

    t and t1 are always diferent! from the debugger: t: + _m_d_name 0x00433890 ".PAVcvehicle@@" t1: + _m_d_name 0x00433850 ".?AVccar@@"

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    • K kfaday

      t and t1 are always diferent! from the debugger: t: + _m_d_name 0x00433890 ".PAVcvehicle@@" t1: + _m_d_name 0x00433850 ".?AVccar@@"

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      jmkhael
      wrote on last edited by
      #8

      yes so check it against t1 dereference first the pointer you receive and then compare it to typeid(ccar) Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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      • J jmkhael

        yes so check it against t1 dereference first the pointer you receive and then compare it to typeid(ccar) Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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        kfaday
        wrote on last edited by
        #9

        Papa wrote: dereference first the pointer you receive and then compare it to typeid(ccar) what do you mean by this? sorry, english isn't my first language

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        • K kfaday

          Papa wrote: dereference first the pointer you receive and then compare it to typeid(ccar) what do you mean by this? sorry, english isn't my first language

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          jmkhael
          wrote on last edited by
          #10

          cvehicle *vtemp=(list->Getvehicle()); if (typeid(*vtemp)==typeid(ccar))) return vtemp; Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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          • J jmkhael

            cvehicle *vtemp=(list->Getvehicle()); if (typeid(*vtemp)==typeid(ccar))) return vtemp; Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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            kfaday
            wrote on last edited by
            #11

            it gives me an error: (runtime error, it builds alright) unhandled exception

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            • K kfaday

              it gives me an error: (runtime error, it builds alright) unhandled exception

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              jmkhael
              wrote on last edited by
              #12

              "If the expression is dereferencing a pointer, and that pointer’s value is zero, typeid throws a bad_typeid exception. If the pointer does not point to a valid object, a __non_rtti_object exception is thrown." Do you have a NULL pointer? Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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              • J jmkhael

                "If the expression is dereferencing a pointer, and that pointer’s value is zero, typeid throws a bad_typeid exception. If the pointer does not point to a valid object, a __non_rtti_object exception is thrown." Do you have a NULL pointer? Papa while (TRUE) Papa.WillLove ( Bebe ) ;

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                kfaday
                wrote on last edited by
                #13

                no, *vtemp isn't null it gives me this warning warning C4541: 'typeid' used on polymorphic type 'class ccar' with /GR-; unpredictable behavior may result

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                • K kfaday

                  Papa wrote: dereference first the pointer you receive and then compare it to typeid(ccar) what do you mean by this? sorry, english isn't my first language

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                  toxcct
                  wrote on last edited by
                  #14

                  you deference a pointer when you don't get the address it contains but when you get what is at the pointed address.

                  char* pc = (char*)malloc(sizeof(char)); // my pointer (something like 0x0A78DQ43)
                  *pc = 'a'; // dereferenced pointer (acsii code for 'a' caracter)

                  pc : simple pointer (cointaining an address)
                  *pc : dereferenced pointer (value at the pointed address)


                  TOXCCT >>> GEII power

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                  • K kfaday

                    no, *vtemp isn't null it gives me this warning warning C4541: 'typeid' used on polymorphic type 'class ccar' with /GR-; unpredictable behavior may result

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                    antlers
                    wrote on last edited by
                    #15

                    typeid depends on RTTI being turned on. RTTI is part of the language standard but C++ turns it off by default. Change your project settings to enable RTTI and you will get rid of the compile-time warning and the run-time exception.

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                    • A antlers

                      typeid depends on RTTI being turned on. RTTI is part of the language standard but C++ turns it off by default. Change your project settings to enable RTTI and you will get rid of the compile-time warning and the run-time exception.

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                      kfaday
                      wrote on last edited by
                      #16

                      that did it!!!!!!!!!!!!!1 thanks!!

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