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Class data member access

manjut19 (65)
Hi,
Iam begginer in programming.I have some doubt regarding class data member accessing in another file.Follwing code showing error.Please correct me.
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class A://file a.cpp
{
public:
int add;
int sub;

};
//file b.cpp
extern class A
void cal()
{
A::add=A::sub;
}
abhishekm71 (820)
- add and sub are not static variables. They can be accessed only through instantiated objects of class A.
- Why do you have a colon after class A in the definition in a.cpp.
- I'm not sure whether you can declare an extern class like the way you have done. Where is your main function?
AbstractionAnon (6954)
Several problems here:

1) Your class A declaration should be in a .h file, not a .cpp file.

2) No : on line 1.

3) You can't declare a class declaration as extern. File b.cpp should #include "a.h"

4) You have to instantiate A somewhere. 
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  A a;

Now, you can refer to a's public variables. 
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  a.add = a.sub;


Last edited on
manjut19 (65)
Ok.Is it correct??
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class A://file a.h
{
public:
int add;
int sub;
 A();//constrcr

};
//file main.cpp
#include "a.h"
class A *pA;
int main()
{
pA=new A();
}
A::A()//costructor
{
sub=10;
cal();
}
//file b.cpp
extern A *pA;
void cal()
{
pA->add=pA->sub;
}
Last edited on
AbstractionAnon (6954)
You still have the extraneous colon on line 1.

File b.cpp also needs a #include a.h"

You have a memory leak because you never release the instance of A that you allocated at line 14.



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