Accessing a Variable

[T RATHA KRISHNAN]

Hi! I've declared a protected variable in a base class. I've assigned value and print the variable in a derived class. It prints correctly. I've printed the same variable inside another derived class. But it prints nothing. How to print the variable that is altered inside another derived class?

[Code o mat]

What do you mean by "it prints nothing"? Show some relevant code, don't forget the <pre> </pre> tags please.

> The problem with computers is that they do what you tell them to do and not what you want them to do. < > "It doesn't work, fix it" does not qualify as a bug report. < > Amazing what new features none of the programmers working on the project ever heard of you can learn about when reading what the marketing guys wrote about it. <

[CPallini]

T.RATHA KRISHNAN wrote:

I've printed the same variable inside another derived class. But it prints nothing.

? :confused: this sample code

#include <iostream>
class A
{
protected:
int a;
public:
A(int a):a(a){}
void show(){ std::cout << "this is A, a=" << a << std::endl;}
};

class B: public A
{

public:
B(int b):A(b){}
void show(){ std::cout << "this is B, a=" << a << std::endl;}
};

class C: public B
{

public:
C(int c):B(c){}
void show(){ std::cout << "this is C, a=" << a << std::endl;}
};

int main()
{
A a(3);
B b(4);
C c(5);

a.show();
b.show();
c.show();

return 0;
}

produces:

this is A, a=3 this is B, a=4 this is C, a=5

:)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[Lost User]

T.RATHA KRISHNAN wrote:

I've declared a protected variable in a base class. I've assigned value and print the variable in a derived class. It prints correctly. I've printed the same variable inside another derived class. But it prints nothing. How to print the variable that is altered inside another derived class?

Are you asking how to share a member variable of base class across different derived classes such that changing in one will reflect in the others?

...byte till it megahertz...

[T RATHA KRISHNAN]

Yes. Exactly what I want.

[AmbiguousName]

i think friend functions can be used.... :)

[Niklas L]

You want a class variable as opposed to an instance variable. A class variable in C++ is declared using the static keyword.

class A
{
protected:
static int my_class_variable;
};

This variable will be shared among all instances of class A and its derived classes.

home

[Lost User]

See what Niklas posted.

...byte till it megahertz...

[Moak]

Read bleedingfingers' answer. :)

Chat in Europe :java: Now with 24% more Twitter

[T RATHA KRISHNAN]

Hi! If I use static as you said, I got the following linker errors: Error 80 error LNK2001: unresolved external symbol "protected: static int CGameState::musicVolume" (?musicVolume@CGameState@@1HA) D:\Goldminer\GameOptionsMenuState.obj

[Lost User]

hey hey hey don't Moak me I had asked the OP a question and before I could reply after my lunch, Niklas had answered it. I find not following up on a question with a reply to be rude and there was no point in re replying.

...byte till it megahertz...

[Lost User]

You have to later initialize it somewhere, for instance, like

int CGameState::musicVolume = 0;

...byte till it megahertz...

[T RATHA KRISHNAN]

I've answered your question.