initialization failure

[thomas]

Hi,

------------code--------------------------------------
#include<iostream>
using namespace std;

class B{
int y;
public:
B(int b=3):y(b){}
int getInt(){
return y;
}
};

class A{
int x;
public:
A(const int &x_){ //Line 1
x=x_;
}
A(B *b){
A(b->getInt()); //Line 2
}
int getInt(){
return x;
}
};

int main(){
B *b = new B;
A *a = new A(b);
cout<<a->getInt()<<endl;
}
---------------------------------------------------------
I expected that in line 2, "b->getInt()" is 3, and by calling
construction function of Line 1, the printed result should be 2;

But it's 0, can anyone tell me the reason? Thanks in advance.

[thomas]

On Oct 1, 4:19*pm, thomas <[e-mail]:

Hi,

------------code--------------------------------------
#include<iostream>
using namespace std;

class B{
* * * * int y;
public:
* * * * B(int b=3):y(b){}
* * * * int getInt(){
* * * * * * * * return y;
* * * * }

};

class A{
* * * * int x;
public:
* * * * A(const int &x_){ * * * * *//Line 1
* * * * * * * * x=x_;
* * * * }
* * * * A(B *b){
* * * * * * * * A(b->getInt()); * * * *//Line *2
* * * * }
* * * * int getInt(){
* * * * * * * * return x;
* * * * }

};

int main(){
* * * * B *b = new B;
* * * * A *a = new A(b);
* * * * cout<<a->getInt()<<endl;}

---------------------------------------------------------
I expected that in line 2, "b->getInt()" is 3, and by calling
construction function of Line 1, the printed result should be 2;

But it's 0, can anyone tell me the reason? Thanks in advance.

ok, got it, cannot call constructor in a constructor.

[sonison.james]

On Oct 1, 4:19*pm, thomas <[e-mail]:

* * * * A(B *b){
* * * * * * * * A(b->getInt()); * * * *//Line *2
* * * * }

---------------------------------------------------------
I expected that in line 2, "b->getInt()" is 3, and by calling
construction function of Line 1, the printed result should be 2;

But it's 0, can anyone tell me the reason? Thanks in advance.

This is because in Line 2, x member of the current object is not being
initialized, instead a new A object is created and it's x is
initialized. You need to simply initialize x of the current object.

A(B *b)
{
// probably have a check to see that b is not NULL before
accessing b ptr
x = b->getInt();
}

Thanks and regards
Sonison James

[puzzlecracker]

ok, got it, cannot call constructor in a constructor.

sure you can, in your case, as someone already mention, you're
creating a new object.

Here is how you can call another ctor

class A{
A(){}
A():this(){

}

};

[Obnoxious User]

On Wed, 01 Oct 2008 06:07:10 -0700, puzzlecracker wrote:

>ok, got it, cannot call constructor in a constructor.

sure you can, in your case, as someone already mention, you're creating
a new object.

Here is how you can call another ctor

class A{
A(){}
A():this(){

}

};

No you can't.

http://www.parashift.com/c++-faq-lit....html#faq-10.3

--
OU
Remember 18th of June 2008, Democracy died that afternoon.
http://frapedia.se/wiki/Information_in_English

[puzzlecracker]

On Oct 1, 11:03 am, Obnoxious User <O...@127.0.0.1wrote:

On Wed, 01 Oct 2008 06:07:10 -0700, puzzlecracker wrote:

ok, got it, cannot call constructor in a constructor.

sure you can, in your case, as someone already mention, you're creating
a new object.

Here is how you can call another ctor

class A{
A(){}
A():this(){

}

};

No you can't.

http://www.parashift.com/c++-faq-lit....html#faq-10.3

--
OU
Remember 18th of June 2008, Democracy died that afternoon.http://frapedia.se/wiki/Information_in_English

Opps, I was referring to calling the base class ctor. Sorry!