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C++ References

 
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onkar
Guest
PostPosted: Wed May 10, 2006 9:21 pm    Post subject: C++ References Reply with quote


I want bi to change as soon as i change ai. How to accomplish this
using references ?

#include<iostream>
using namespace std;
class B
{
private:
int bi;
public:
B()
{
bi=10;
}
int& get_bi()
{
return bi;
}
void display()
{
cout<<"bi = "<<bi<<endl;
}
};
class A
{
private:
B b;
int ai;
public:
A()
{
ai=b.get_bi();
}
void assign(int i)
{
ai=i;
}
void display()
{
cout<<"ai = "<<ai<<endl;
}
};
int main()
{
B bo;
bo.display();

A ao;
ao.display();
ao.assign(1111);
ao.display();
bo.display();

return 0;
}


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Carl Barron
Guest
PostPosted: Thu May 11, 2006 6:21 pm    Post subject: Re: C++ References Reply with quote


In article <1147258067.199029.103000 (AT) i39g2000cwa (DOT) googlegroups.com>,
onkar <onkar.n.m (AT) gmail (DOT) com> wrote:

Quote:
I want bi to change as soon as i change ai. How to accomplish this
using references ?

#include<iostream
using namespace std;
class B
{
private:
int bi;
public:
B()
{
bi=10;
}
int & get_bi() {return bi;}
[snip]
};
class A
{
private:
B b;
int ai;
public:
A()
{
ai=b.get_bi();
[snip]

class A
{
B b;
int &ai;
public:
A() :b(),a(b.get_bi()){}
};

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Ben Cottrell
Guest
PostPosted: Thu May 11, 2006 6:21 pm    Post subject: Re: C++ References Reply with quote


onkar wrote:
Quote:
I want bi to change as soon as i change ai. How to accomplish this
using references ?


Declare bi as a reference, and initialise it to ai in the constructor.
Similar to this example:

class base
{
int a;
protected:
int& getA() {return a;}
};

class derived : public base
{
int& b;
public:
derived() : b(getA()) {}
};

note that the changes go both ways, because effectively, they are both
alternative names for the same object.

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Zara
Guest
PostPosted: Thu May 11, 2006 11:25 pm    Post subject: Re: C++ References Reply with quote
On 10 May 2006 17:02:31 -0400, "onkar" <onkar.n.m (AT) gmail (DOT) com> wrote:

Quote:
I want bi to change as soon as i change ai. How to accomplish this
using references ?

#include<iostream
using namespace std;
class B
{
private:
int bi;
public:
B()
{
bi=10;
}
int& get_bi()
{
return bi;
}
void display()
{
cout<<"bi = "<<bi<<endl;
}
};
class A
{
private:
B b;
int ai;
chage to:

int& ai;
So that it really is a reference, not a value by itself
Quote:
public:
A()
{
ai=b.get_bi();
}
change to:

a():ai(b.get_bi()) {}
The reference must be initialized on the constructor list, or you
should get an error from the compiler. From now on, any change to ai
will change the value of the object referred by ai (in this case, bi).

Quote:
void assign(int i)
{
ai=i;
}
void display()
{
cout<<"ai = "<<ai<<endl;
}
};
...


Regards,

Zara

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