Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Returning an Object in a function

Posted on 2006-11-25
2
Medium Priority
?
202 Views
Last Modified: 2010-04-01
Hi Experts,

I have the following.  In getB( ) function when I return the Object b, would I have any problems.  I think If I do " B b = new B( ); " and returning &b would cause problem as the function returns, b goes out of scope.  Is it true even in my case?
 

class A
{

};

class B
{

};

class C
{
public:
     C( A& aa);
     B& getB( );  
private:
    A * m_aa;
};

B& C::getB( )
{
     B b;
    //do some initialization of B here
    return b;
}
0
Comment
Question by:ambuli
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
2 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 1200 total points
ID: 18012256
There are several options depending on what members B contains. If they are just plain data, you could

B C::getB( ) // return an instance, not a reference
{
     B b;
    //do some initialization of B here
    return b;
}

void C::getB(B& r )
{
     B b;
    //do some initialization of B here
    r = b;
}

The same applies if you have more complex members, however you night need a copy constructor (http://en.wikipedia.org/wiki/Copy_constructor) and assignement operator (http://en.wikipedia.org/wiki/Assignment_%28computer_science%29). See also http://en.wikipedia.org/wiki/Object_copy
0
 
LVL 86

Expert Comment

by:jkr
ID: 18012280
Oh, and you are right

B* C::getB( )
{
     B* b = new B;
    //do some initialization of B here
    return b;
}

would also be an option, yet that would require more attention about deleting the objects. Also

B& C::getB( )
{
     B b;
    //do some initialization of B here
    return b;
}

will *not* work, since the reference returned would be invalid as soon as the function exits.
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
Introduction This article is the first in a series of articles about the C/C++ Visual Studio Express debugger.  It provides a quick start guide in using the debugger. Part 2 focuses on additional topics in breakpoints.  Lastly, Part 3 focuses on th…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.

722 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question