Passing a node as an outstream operator

Question

This prints an error message about qualifiers but don't really understand what that means and how to adjust the code for it to work? Anyways, thanks a lot for looking at the code.

Note: The ostream operator is friended in the Node class.

using namespace std;

ostream& operator(ostream& output, const Node* currentNode)
{
   return output;
}

void Node::nodeFunction()
{
   //This node has items attached to the 'this' statement. After
   //the necessary functions, this is called to output the items.

   cout << this;
}

So it's not possible to do it from this standpoint? Is it best to simply call out each of them in turn from the node function itself? — Jason A., Jul 17 '11 at 05:36

score 0 · Answer 1 · answered Jul 17 '11 at 05:20

0

The & on the return value of the operator is in the wrong place, and it's generally better to use references rather than pointers for ostream operators:

ostream& operator<<(ostream &output, const Node &currentNode)
{
    // Output values here.
    return output;
}

void Node::nodeFunction()
{
     cout << *this;
}

answered Jul 17 '11 at 05:20

Sven

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Wish I could use references, but I don't have a choice. I really appreciate the code, but the same errors came up when I tried calling to the items using the currentNode parameter. – Jason A. Jul 17 '11 at 05:27
passing âconst Nodeâ as âthisâ argument of âstd::string Node::getFirstName()â discards qualifiers – Jason A. Jul 17 '11 at 05:38
I tried using currentNode->getFirstName() within the operator – Jason A. Jul 17 '11 at 05:39

Alok Save · Accepted Answer · 2011-07-17T05:48:54.793

Your overloaded stream operator declaration should be like this:

std::ostream& operator<<(std::ostream& os, const T& obj);
^^^^^^^^^^^^^

You should be returning a reference to object of std::ostream, the & is wrongly placed in your overloaded function prototype.

Have a look at the working sample here.

Adding the source code here, for completeness.
Note: I have taken class Node members as public for ease of demonstration.

#include<iostream>

using namespace std;

class Node
{
    public: 
    int i;
    int j;
    void nodeFunction();

    friend ostream& operator <<(ostream& output, const Node* currentNode);     
};

ostream& operator<<(ostream& output, const Node* currentNode)
{
   output<< currentNode->i;
   output<< currentNode->j;

   return output;
}

void Node::nodeFunction()
{
   //This node has items attached to the 'this' statement. After
   //the necessary functions, this is called to output the items.

   cout << this;
}

int main()
{
    Node obj;
    obj.i = 10;
    obj.j = 20;

    obj.nodeFunction();

    return 0;
}

I'm using the namespace std, does that clear it up? I'm sorry I didn't mention that in the code. — Jason A., Jul 17 '11 at 05:32
@Jason A.:See the edited answer, Added a compilable, working copy of what you are trying to acheive. — Alok Save, Jul 17 '11 at 05:39

Passing a node as an outstream operator

2 Answers2