operator overloading : getting unidentifiable errors

Question

#include <iostream>
using namespace std;

class sales_item  
{  
    friend ostream& operator<<(ostream&,const sales_item&);

public:

    int item;
    sales_item()
    {
        item=2;
    }
    sales_item operator+(sales_item& item1)
    {
        sales_item item2;
        item2.item = item1.item+item;
        return item2;
    }
};



ostream& operator<<(ostream &out, sales_item& item3)  
{

    out<<item3.item;
    return out;
}

int main(int argc, const char * argv[])  
{  
    sales_item item1,item2;
    sales_item item3=(item1+item2);
    cout<<item3;
    return 0;
}

in this program i am overloading the + and << operators. but when im trying to replace the line cout << item3 ; with cout << (item1+item2) ; or cout << item1+item2 ;

i am getting the following errors :

Undefined symbols for architecture x86_64:
  "operator<<(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, sales_item const&)", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

How is it happening?

How are the errors unknown if you posted them?

Qaz
– Qaz

2013-01-07 11:31:18 +00:00
Commented Jan 7, 2013 at 11:31 — Qaz
– Qaz, Commented Jan 7, 2013 at 11:31

Luchian Grigore · Accepted Answer · 2013-01-07 11:31:52Z

6

You implemented

ostream& operator<<(ostream &out, sales_item& item3)

vs

friend ostream& operator<<(ostream&,const sales_item&);
//                                    ^
//                        const is missing in definition

answered Jan 7, 2013 at 11:31

Luchian Grigore

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2 Comments

JTN Over a year ago

i removed the const at both the places. still i got an error. : invalid operands to the binary expression.

Luchian Grigore Over a year ago

@jithinc don't remove const - the signature should be ostream& operator<<(ostream &out, const sales_item& item3) in both places.

JTN · Accepted Answer · 2013-01-07 11:46:51Z

0

hey the error was because i was referencing the sales item in the function ostream& operator<<(ostream &out,sales_item &item3); when i removed the & it started working fine.. thanks

answered Jan 7, 2013 at 11:46

JTN

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1 Comment

Angew is no longer proud of SO Over a year ago

But it's (most likely) not doing what you want it to. It's now creating a copy when calling the function. Just as Luchian said, you should have const & in both places.

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