Use variable in another class

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Class B is instantiated in class A:

Class A {
int x, y;

B b;
}

How can I use variables x and y from member functions of class B?

Posted 23-Apr-10 11:46am

wctechbdm

Updated 23-Apr-10 23:20pm

Moak

v3

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Adam Roderick J · Accepted Answer · 2010-04-24T01:36:00

I think, it better if you get some more knowledge regarding class design.
So i prefer you to have a look with some book in C++ like C++ Primer from Stanley B Lippman.

Well see your case

class B
{
public:
  void SetAVal( int X1, int Y1 )
  {
     LocalX = X1;
     LocalY = Y1;
  }
private:
   int LocalX, LocalY;
};

Class A {
int x, y;
void SetValTOB()
{
  b.SetAVal( x, y );
}

B b;
}

Christian Graus · Accepted Answer · 2010-04-23T18:23:00

You should buy a book on C++ and read the chapters on how object oriented programming works. Your question makes no sense. Class A has no variables, instances of class A do. If B has an instance of A, it can access the variables in A. A has an instance of B here, and can access values in it, if they are public. You'd have to pass the instance of A into the function in B, or pass the x/y values in directly. It can't access them otherwise.

Saurabh.Garg · Accepted Answer · 2010-04-23T15:08:00

Solution 2

You cannot directly use variables declared in A in any other class, whether nested or not. You will have to pass an instance of A and then use member functions of A to access its variables.

-Saurabh

Posted 23-Apr-10 15:08pm

Saurabh.Garg

supercat9 · Accepted Answer · 2010-04-23T12:11:00

Since B knows nothing about the classes into which it may be instantiated, it has no way of knowing whether such classes will always, never, or sometimes, have fields named 'x' and 'y'.

What you need to do, I think, is have the object of class A tell class B about itself when instantiating B (e.g. by having B take a parameter of type A in its constructor). Class B would then be able to use any public methods or properties of the item of class A that was passed in.

The Manoj Kumar · Accepted Answer · 2010-04-24T17:15:00

Solution 5

I think your question is very basic and if you will read a little more about classes in c++ then you will get the answer yourself. Just read a bit more, don't jump to the exercises at the end of chapter or to your project :) .

Posted 24-Apr-10 17:15pm

The Manoj Kumar

Use variable in another class

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