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friend cannot access private variable

 
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Gary Wessle
Guest
PostPosted: Wed Aug 09, 2006 9:10 am    Post subject: friend cannot access private variable Reply with quote


Hi

I am trying to call a function of a class which declares an object of
another class and return its private member.


thanks

****************************************************************
int main(){
strategy1 m;
cout << m.get_balance() << endl;
}

****************
class strategy1 //interface
{
public:
double get_balance();
strategy1();
};

****************//implementation
strategy1::strategy1(){
cout << "strategy1 called" << endl;
}

double strategy1::get_balance(){
Account a;
return a.balance;
}

****************
class Account //interface
{
class strategy1;
friend class strategy1;

double balance; //<<--error line no. 12

public:
....
};

the error I am getting is

**************** error ****************
Account.h:12: error: 'double Account::balance' is private
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Sumit RAJAN
Guest
PostPosted: Wed Aug 09, 2006 9:10 am    Post subject: Re: friend cannot access private variable Reply with quote


Gary Wessle wrote:
Quote:
Hi

I am trying to call a function of a class which declares an object of
another class and return its private member.


thanks

****************************************************************
int main(){
strategy1 m;
cout << m.get_balance() << endl;
}

****************
class strategy1 //interface
{
public:
double get_balance();
strategy1();
};

****************//implementation
strategy1::strategy1(){
cout << "strategy1 called" << endl;
}

double strategy1::get_balance(){
Account a;
return a.balance;
}

****************
class Account //interface
{
class strategy1;
friend class strategy1;

double balance; //<<--error line no. 12

public:
...
};

the error I am getting is

**************** error ****************
Account.h:12: error: 'double Account::balance' is private


#include <iostream>

class strategy1;

class Account //interface
{
friend class strategy1;
double balance;

public:
Account() : balance(0.0) {}
};

class strategy1 //interface
{
public:
double get_balance();
strategy1();
};


strategy1::strategy1(){
std::cout << "strategy1 called" << std::endl;
}

double strategy1::get_balance(){
Account a;
return a.balance;
}




int main(){
strategy1 m;
std::cout << m.get_balance() << std::endl;
}

Note that I have added a constructor for Account. I have also rearranged
some of you definitions.

Regards,
Sumit.
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Gary Wessle
Guest
PostPosted: Wed Aug 09, 2006 9:10 am    Post subject: Re: friend cannot access private variable Reply with quote


Sumit RAJAN <sumit.rajan (AT) gmail (DOT) com> writes:

Quote:
Sumit RAJAN wrote:


#include <iostream

class strategy1;

Also note that the above forward declaration is not really required.

Sumit.

thank you
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I V
Guest
PostPosted: Wed Aug 09, 2006 9:10 am    Post subject: Re: friend cannot access private variable Reply with quote
On Wed, 09 Aug 2006 15:30:44 +1000, Gary Wessle wrote:
Quote:
I am trying to call a function of a class which declares an object of
another class and return its private member.

[...]

****************
class Account //interface
{
class strategy1;

This declares a class Account::strategy1, which shadows the class
::strategy1 .

Quote:
friend class strategy1;

This makes the class Account::strategy1 a friend of Account. ::strategy1
is _not_ made a friend here.

Quote:
[...]

Account.h:12: error: 'double Account::balance' is private

Because the friend class here is Account::strategy1, not ::strategy1 .
Move the forward declaration of strategy1 outside of the definition of
Account, and it should compile.
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Sumit RAJAN
Guest
PostPosted: Wed Aug 09, 2006 9:10 am    Post subject: Re: friend cannot access private variable Reply with quote
Sumit RAJAN wrote:

Quote:

#include <iostream

class strategy1;

Also note that the above forward declaration is not really required.

Sumit.
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