member variable initialization

George_George

Hello everyone, I am wondering in the following code, member variable a in class B is not put in the initialization list or constructor of B directly, but it is initialized. How and when member variable a of class B is created and initialized? Is constructor of B invokes constructor of a? Output is, In constructor A In constructor B
using namespace std; class A { public: A() { cout << "In constructor A" << endl; } }; class B { public: A a; B() { cout << "In constructor B" << endl; } }; int main() { B b; return 0; }

thanks in advance, George

CPallini

You can find all answers here http://msdn2.microsoft.com/en-us/library/kstd9k24(vs.71).aspx[^] :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

George_George

Thanks CPallini, My question is answered. regards, George

George L Jackson

Order of the member variables affects initialization. Play around with the order of the A and B member variables in C:

#include <iostream>

using std::wcout;
 
class A
{
public:
	A()
	{
		wcout << L"A\n";
	}
};
 
class B
{
public:
	B()
	{
		wcout << L"B\n";
	}
};
 
class C
{
	A a;
	B b;
public:
	C() : a()
	{
		wcout << L"D\n";
	}
};
 
int _tmain(int argc, _TCHAR* argv[])
{
	C c;
 
	wcout << L"End\n";
}

More constructor information: http://www.parashift.com/c++-faq-lite/ctors.html[^] Free e-books: http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html[^]

"We make a living by what we get, we make a life by what we give." --Winston Churchill

modified on Tuesday, December 18, 2007 10:40:05 AM

George_George · modified on Tuesday, December 18, 2007 10:40:05 AM

Thanks George, The output is, A B D End. But I do not know what do you want to prove? Any more descriptions please? regards, George

toxcct · modified on Tuesday, December 18, 2007 10:40:05 AM

please, George, don't give too much to George_George. he's been abusing this board for several months, and he doesn't even search the web before asking very simple question. so, please, don't give him too easy answers...

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toxcct

George_George wrote:

I do not know what do you want to prove?

are you stupid ? you have the order of execution, so you can deduce from there the order in which the members are initialized... :doh:

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CPallini

perhaps a stronger example could be

...
public:
C() : b()
{
wcout << L"D\n";
}
...

:)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

CPallini

toxcct wrote:

are you stupid ?

You're definitely unable to be patient with that guy! :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

toxcct

PATIENT ? WTF !!! i've been waiting 1 year and a half for an answer to a question of mine, and you call me not patient ? :mad:

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CPallini

toxcct wrote:

i've been waiting 1 year and a half for an answer to a question of mine, and you call me not patient ?

and did he eventually give it? :rolleyes:

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

toxcct

eventually ? have you ever seen that monkey replying to one of your questions ? but you know, those chinese people (i mean, the ones living in china) have so much restrictions over their head by their governement that i wouldn't be astonished that they are feared to give too much personal informations. anyway, i definitely know a good one about him : George_George is a prat, a moron, wait, A DICKHEAD !! someone with a minimal common sense wouldn't reask same things again and again.

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CPallini

toxcct wrote:

have you ever seen that monkey replying to one of your questions ?

Yes, he did. I understand you're angry with him, but... be patient. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

toxcct

CPallini wrote:

Yes, he did.

where ? and about what ? if it was about a technical question, yes, he will sometimes answer. about personnal question, never. and not only he doesn't reply not really exactly, but he totally ignore us.

CPallini wrote:

I understand you're angry with him, but... be patient.

as long as he continue in his direction, I have absolutely no reason to change my idea of this guy. it's up to him to show me a better side of his.

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George L Jackson

Change the order of A and B in the C class and see the result:

class C
{
	B b;
	A a;
public:
	C() : a()
	{
		wcout << L"D\n";
	}
};

"We make a living by what we get, we make a life by what we give." --Winston Churchill

George L Jackson

Toxcct, I understand your pain, and have been following George_George exploits. He bites the hand that feeds him! However, my goal is to help and I won't let posters such as George_George change my focus just because he is a SOAB. Geo

"We make a living by what we get, we make a life by what we give." --Winston Churchill

toxcct

George L. Jackson wrote:

just because he is a SOAB

lol, i feel lighter now that someone else have the same feeling than me. BTW, I do have the same goal too, and I generally answer his technical questions, but there a time when he already has enough to find his answer. it's not our job to pound out a full working code. we are here to advice and to help when others are in real need. posting just to post is not my religion.

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modified on Tuesday, December 18, 2007 10:33:26 AM

CPallini

toxcct wrote:

where ? and about what ?

I asked him what is the reason behind all his questions. He answered was just for technical fun.

toxcct wrote:

I have absolutely no reason to change my idea of this guy

Oh, you don't have to. But I think you could just be more patient with him. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.

David Crow

toxcct wrote:

it's up to him to show me a better side of his.

By telling you his age? How exactly does that matter to anything? :confused:

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

CPallini

DavidCrow wrote:

By telling you his age?

Or if he comes from China? Well I think toxcct is just a curious guy. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.