Programming Forums > Application Development > C++

Kilo · Nov 21st, 2005, 11:19 AM

im LOST.... how can i take a base pointer and look into the object of a derived class... Thanks!

DaWei · Nov 21st, 2005, 11:50 AM

MS VC++ is a compiler, not a language. It does a creditable job with polymorphism, pretty much what you'd expect. Is there a particular piece of code you have in mind, and a particular failure mechanism?

Kilo · Nov 21st, 2005, 12:35 PM

Quote:

Originally Posted by DaWei

MS VC++ is a compiler, not a language. It does a creditable job with polymorphism, pretty much what you'd expect. Is there a particular piece of code you have in mind, and a particular failure mechanism?

im not stupid bro. MSVC++ is the only compiler that gives me this error for one language....

example:

(Toggle Plain Text)

class Base
{
     public:
          Base() {;}
          virtual ~Base() {;}

          virtual void show()
          {
                 cout << "Test Base." << endl;
          }
};

class Derived:Base
{
     public:
          Derived() {;}
          virtual ~Derived() {;}

          void show()
          {
                 cout << "Test Derived." << endl;
          }
};

int main()
{
     Base B;
     Derived D;

     Base *P;           //my base pointer

     P=&B;              //works
     P->show();       //works

     P=&D;              //creates an error
     P->show();
     
     return 0;
}

if i cannot do this. its not polymorphism!!!!

grumpy · Nov 21st, 2005, 12:42 PM

The reason for the error is that inheritence of classes is private by default in C++. If other compilers are accepting your code without complaint, then those compilers are broken.

Try changing the inheritence to

(Toggle Plain Text)

class Derived:  public Base
{
     // etc
}

Kilo · Nov 21st, 2005, 12:45 PM

Quote:

Originally Posted by grumpy

The reason for the error is that inheritence of classes is private by default in C++. Try changing the inheritence to

(Toggle Plain Text)

class Derived:  public Base
{
     // etc
}

that makes complete sense.... let me go ahead and try that and i will get back to you! Thanks!

Kilo · Nov 21st, 2005, 1:00 PM

works great thanks a ton

DaWei · Nov 21st, 2005, 1:32 PM

Quote:

im not stupid bro.

I'm not your bro. More likely your granddaddy. Sorry your compiler was broken, though.

Kilo · Nov 21st, 2005, 6:45 PM

Quote:

Originally Posted by DaWei

I'm not your bro. More likely your granddaddy. Sorry your compiler was broken, though.

you could be my granddaddy bro? It wasn't broken lol, its was my fault i completely forgot about specifying wether or not the base class was public or private... How long have you been programming man? My grandfather has been since back in the day and (he uses COBOL) when they wanted him to learn Delphi he quit lol!

DaWei · Nov 21st, 2005, 6:50 PM

I'm not really a programmer, that was just a subset tool. I'm a retired 64-year old EE.

Kilo · Nov 21st, 2005, 8:49 PM

EE = electronic engineer? i need to get a degree in that also... so that i can soder(sp) my programs to a bread board

Nov 21st, 2005, 11:19 AM	#1
Kilo Expert Programmer Join Date: Nov 2005 Location: In Pink Clam? Posts: 542 Rep Power: 0	Msvc++ = No Polymorphism??? im LOST.... how can i take a base pointer and look into the object of a derived class... Thanks! __________________ "When in Rome, Do as the Romans Do" "Beauty is in the eye of the BEER holder" "Save your breath your going to need it for your blow up doll later" SearchLores.org

Nov 21st, 2005, 11:50 AM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	MS VC++ is a compiler, not a language. It does a creditable job with polymorphism, pretty much what you'd expect. Is there a particular piece of code you have in mind, and a particular failure mechanism? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 21st, 2005, 12:42 PM	#4
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	The reason for the error is that inheritence of classes is private by default in C++. If other compilers are accepting your code without complaint, then those compilers are broken. Try changing the inheritence to (Toggle Plain Text) class Derived: public Base { // etc } class Derived: public Base { // etc }

Nov 21st, 2005, 1:00 PM	#6
Kilo Expert Programmer Join Date: Nov 2005 Location: In Pink Clam? Posts: 542 Rep Power: 0	works great thanks a ton __________________ "When in Rome, Do as the Romans Do" "Beauty is in the eye of the BEER holder" "Save your breath your going to need it for your blow up doll later" SearchLores.org

Nov 21st, 2005, 6:50 PM	#9
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	I'm not really a programmer, that was just a subset tool. I'm a retired 64-year old EE. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 21st, 2005, 8:49 PM	#10
Kilo Expert Programmer Join Date: Nov 2005 Location: In Pink Clam? Posts: 542 Rep Power: 0	EE = electronic engineer? i need to get a degree in that also... so that i can soder(sp) my programs to a bread board __________________ "When in Rome, Do as the Romans Do" "Beauty is in the eye of the BEER holder" "Save your breath your going to need it for your blow up doll later" SearchLores.org

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Programming Forums > Application Development > C++

Msvc++ = No Polymorphism???