Solved

C++: << Operator does not work as expected

Posted on 2010-11-16
7
377 Views
Last Modified: 2012-05-10
I am trying to overload the << operator.

I have a custom class called person.

I added this to person.h:

public:
.....
....
ostream &person::operator<<(ostream &stream);

I added this to person.cpp
....
....
ostream &person::operator<<(ostream &stream) {
            stream << this->getAge()  << " ";
            return stream;
      }

In the main function, I did the following.
person P4 = person("C", "C", 23); //first name, last name and age
cout << &P4 << " ";

The code compiles fine but when I run the code, I see this output:
0012FDFC

I am expecting output:
23

I am using Visual Studio 2008.

Not sure what am I doing wrong. Please help. Thanks in advance.
0
Comment
Question by:shekhar_shashi
  • 4
  • 2
7 Comments
 
LVL 44

Assisted Solution

by:AndyAinscow
AndyAinscow earned 100 total points
ID: 34149200
&P4 means the memory adress of P4

does this do what you expect
cout << P4 << " ";
0
 
LVL 3

Author Comment

by:shekhar_shashi
ID: 34149276
If I change the code this way, I get this compilation error:

error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'person' (or there is no acceptable conversion)      
0
 
LVL 86

Accepted Solution

by:
jkr earned 400 total points
ID: 34149422
That's what evilrix' point was in your last question - you better make that
class person; // foward declaration



ostream& operator<< ( ostream& os, const student& p) ;



class person

{

  friend ostream& operator<< ( ostream& os, const person& p) ;



  // ...



};



ostream& operator<< ( ostream& os, const person& p)

{

  os << p.getAge();



  return 0s;

}

Open in new window

0
Threat Intelligence Starter Resources

Integrating threat intelligence can be challenging, and not all companies are ready. These resources can help you build awareness and prepare for defense.

 
LVL 3

Author Comment

by:shekhar_shashi
ID: 34149717
Pardon my C++ ignorance here.

I am getting about 9 compilation errors after making these code changes.

Instead of posting all the compilation errors, let me ask a few questions:

Question 1:
Where should the forward declaration go?

class person; // foward declaration

ostream& operator<< ( ostream& os, const student& p) ;

Question 2: I am guessing this code needs to be placed in the header file.

class person
{
  friend ostream& operator<< ( ostream& os, const person& p) ;

  // ...

};

Am I correct?

Question 3:

I am guessing this code will be placed in the person.cpp file.

ostream& operator<< ( ostream& os, const person& p)
{
  os << p.getAge();

  return 0s;
}
 
Am I correct?

Thanks.


0
 
LVL 86

Assisted Solution

by:jkr
jkr earned 400 total points
ID: 34149837
1. Just above the operator's declaration

2. Actually, you just need to add
  friend ostream& operator<< ( ostream& os, const person& p) ;

to the declaration of the 'person' class.

3. You're absolutely correct ;o)
0
 
LVL 3

Author Comment

by:shekhar_shashi
ID: 34149879
Your answer was spot on.  Thanks a bunch for helping out this C++ newbie.
0
 
LVL 3

Author Closing Comment

by:shekhar_shashi
ID: 34149904
Thanks
0

Featured Post

Do You Know the 4 Main Threat Actor Types?

Do you know the main threat actor types? Most attackers fall into one of four categories, each with their own favored tactics, techniques, and procedures.

Join & Write a Comment

Often, when implementing a feature, you won't know how certain events should be handled at the point where they occur and you'd rather defer to the user of your function or class. For example, a XML parser will extract a tag from the source code, wh…
C++ Properties One feature missing from standard C++ that you will find in many other Object Oriented Programming languages is something called a Property (http://www.experts-exchange.com/Programming/Languages/CPP/A_3912-Object-Properties-in-C.ht…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
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.

708 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

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now