Question

I have a string class in my c++ project. I have to use double linked list and make my own string class. In my string class I have to overload <, > and == operators. Actually I did this. But in my other class I have a listing function which compares my string classes. In this comparison I had “taking address of temporary” error.

Here is my string class:

#include "String.h"

String::String(int coming)
{
   x=coming;
}

int  String::getX()
{
    return x;
}

String String::operator==(String *taken)
{
    return String (x==taken->x);
}

and here is my listing method:

void myclass::list(String *taken)
{
    otherclass *temp=head;

    while(temp!=NULL)
    {
        if(&temp->get_string()==taken)//where i get error message.
            cout<<temp<<endl;
        temp=temp->get_nextnode();
    }
}

Answer 1

The compiler is telling you precisely the problem: you cannot take the address of a temporary object. temp->get_string() is a temporary object¹, and you are trying to take its address.

I’m not really sure what your aim is here, so I can’t suggest a fix. But I would strongly suggest that defining String::operator== to take a pointer as the right-hand side will lead to confusion. And having it return another String makes little sense either; normally one would expect == to evaluate to a boolean value.

---

_{1. Well, presumably. You haven’t shown the declaration of get_string().}