C++ No << operator found which takes right-hand operand - c++

Question

I am working on some C++ homework and have hit a snag, I cannot run my displayList() function in my linkedlist class. I receive the following error.
Error 1 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'weatherstats' (or there is no acceptable conversion) c:\users\larry\documents\visual studio 2013\projects\weatherstats\weatherstats\linkedlist.h 100 1 WeatherStats
So I need to overload the << operand but I have tried using a few examples I found online but with no luck. Can someone help me with my << overload operator please?
EDIT: Added Weatherstats.cpp
EDIT 2: I created an overloaded << operand in my weatherstats.cpp file, I updated my content below. Instead of outputting my data, it outputs all data I enter as 1. I enter 2 for snow and it prints out 1 when using my displayList() function.
linkedlist.h
#pragma once
#include"WeatherStats.h"
#include<iostream>
#include<string>
using namespace std;
template <class T>
class linkedlist
{
private:
struct ListNode
{
T value; //Current value of node
struct ListNode *next; //Pointer to next node
};
ListNode *head; //Head pointer
public:
/*!
Constructors
!*/
linkedlist()
{
head = NULL;
};
/*!
Destructors
!*/
~linkedlist();
/*!
Prototypes
!*/
void appendNode(T); //Append a node to list
void insertNode(T); //Insert a node to list
void deleteNode(T); //delete a node in list
void searchList(T); //Search a node in list
void displayList() const; //Display the full list
friend ostream &operator << (ostream&, linkedlist<T> &);
};
//**
//Append Node
//**
template <class T>
void linkedlist<T>::appendNode(T newValue)
{
ListNode *newNode; //Point to new node
ListNode *nodePtr; //Move through list
//Assign newValue to new node
newNode = new ListNode;
newNode->value = newValue;
newNode->next = NULL;
if (!head)
{ //If empty assign new node as head
head = newNode;
}
else
{ //Assign head to nodePtr
nodePtr = head;
//Find last node in list
while (nodePtr->next)
{
nodePtr = nodePtr->next;
}
//Insert newNode as the last node
nodePtr->next = newNode;
}
}
//**
//Display List
//**
template <class T>
void linkedlist<T>::displayList()const
{
ListNode *nodePtr;
//Assign head to nodePtr
nodePtr = head;
//While nodePtr pointing to a node, print to screen
while (nodePtr)
{
//Print value
cout << nodePtr->value << endl; //ERROR C2679 HERE
//Move nodePtr to next node
nodePtr = nodePtr->next;
}
}
//**
//Insert Node
//**
template <class T>
void linkedlist<T>::insertNode(T newValue)
{
ListNode *newNode;
ListNode *nodePtr;
ListNode *previousNode = NULL;
//New node
newNode = new ListNode;
newNode->value = newValue;
//If list is empty assign newValue to head
if (!head)
{
head = newNode;
newNode->next = NULL;
}
else
{
//Assign head to nodePtr
nodePtr = head;
//Pass over all nodes who are less than newValue
while (nodePtr != NULL && nodePtr->value < newValue)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
//If new node will be first, insert before all other nodes
if (previousNode == NULL)
{
head = newNode;
newNode->next = nodePtr;
}
else
{
previousNode->next = newNode;
newNode->next = nodePtr;
}
}
}
//**
//Delete Node
//**
template <class T>
void linkedlist<T>::deleteNode(T searchValue)
{
ListNode *nodePtr; //Traverse our list
ListNode *previousNode = NULL; //Points to previous node
//Check if list is empty
if (!head)
{
cout << "This list is empty." << endl;
return;
}
//Delete head if == searchValue
if (head->value == searchValue)
{
nodePtr = head->next;
cout << head->value << " deleted" << endl;
delete head;
head = nodePtr;
}
else
{
//Set nodePtr to head
nodePtr = head;
//Skip nodes not equal num
while (nodePtr != NULL && nodePtr->value != searchValue)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
//Link previous node to the node after nodePtr and then delete
if (nodePtr)
{
previousNode->next = nodePtr->next;
cout << nodePtr->value << " deleted" << endl;
delete nodePtr;
}
}
}
//**
//Search List
//**
template <class T>
void linkedlist<T>::searchList(T searchValue)
{
ListNode *nodePtr; //Traverse our list
ListNode *previousNode = NULL; //Points to previous node
int counter = 0;
//Check if list is empty
if (!head)
{
cout << "This list is empty." << endl;
return;
}
//Check if head == searchValue
if (head->value == searchValue)
{
cout << head->value << " found at position 0" << endl;
}
else
{
//set nodePtr to head
nodePtr = head;
//Pass over all nodes that do not equal searchValue
while (nodePtr != NULL && nodePtr->value != searchValue)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
counter++;
}
//When nodePtr == searchValue
if (nodePtr)
{
cout << nodePtr->value << " found at position " << counter << endl;
}
else
{
cout << "-1: Value not found." << endl;
}
}
}
//**
//Destructor
//**
template <class T>
linkedlist<T>::~linkedlist()
{
ListNode *nodePtr; // To traverse the list
ListNode *nextNode; // To point to the next node
// Position nodePtr at the head of the list.
nodePtr = head;
// While nodePtr is not at the end of the list...
while (nodePtr != NULL)
{
// Save a pointer to the next node.
nextNode = nodePtr->next;
// Delete the current node.
delete nodePtr;
// Position nodePtr at the next node.
nodePtr = nextNode;
}
}
template <class T>
ostream &operator << (ostream stream, linkedlist<T> &obj)
{
stream >> obj.value;
return stream;
}
main.cpp
#include "linkedlist.h"
#include "WeatherStats.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
int int_numMonths; //Hold number of months value
double dbl_rain; //Hold rain value
double dbl_snow; //Hold snow value
double dbl_sunnyDays; //Hold sunny days value
//Create lnk_list object with weatherstats
linkedlist<weatherstats>weather_list;
cout << "Weather Data" << endl;
cout << endl;
cout << "What is the number of months you want to enter data for?: ";
cin >> int_numMonths;
cout << endl;
//Loop to enter each months values
for (int i = 0; i < int_numMonths; i++)
{
cout << "Month " << i + 1 << endl;
cout << "Enter amount of rain: " << endl;
cin >> dbl_rain;
cout << "Enter amount of snow: " << endl;
cin >> dbl_snow;
cout << "Enter number of Sunny Days: " << endl;
cin >> dbl_sunnyDays;
//Create weatherstats obj and pass it rain,snow and sunnyDays
weatherstats month_data(dbl_rain,dbl_snow,dbl_sunnyDays);
weather_list.appendNode(month_data);
}
weather_list.displayList();
}
Weatherstats.cpp
#include "WeatherStats.h"
#include <iostream>
using namespace std;
/*!
Constructors
!*/
weatherstats::weatherstats()
{
dbl_rain = 0;
dbl_snow = 0;
dbl_sunnyDays = 0;
}
weatherstats::weatherstats(double r, double s, double d)
{
dbl_rain = r;
dbl_snow = s;
dbl_sunnyDays = d;
}
/*!
Accessors
!*/
double weatherstats::getRain()
{
return dbl_rain;
}
double weatherstats::getSnow()
{
return dbl_snow;
}
double weatherstats::getsunnyDays()
{
return dbl_sunnyDays;
}
/*!
Mutators
!*/
void weatherstats::setRain(double r)
{
dbl_rain = r;
}
void weatherstats::setSnow(double s)
{
dbl_snow = s;
}
void weatherstats::setsunnyDays(double d)
{
dbl_sunnyDays = d;
}
//Overload Opperator
ostream& operator << (ostream &stream, weatherstats &obj)
{
stream <<&weatherstats::getRain << " - " << &weatherstats::dbl_snow << " - " << &weatherstats::getsunnyDays << endl;
return stream;
}

Answer 1

I'm going to take a stab in the dark with this, as I haven't touched templates or overloading for a couple of years.
Do you have the << operator overloaded for your weatherstats class?
Your error line is trying to print the value member variable. In your ListNode definition you say value is of type T (i.e. a template).
In your main() you are creating a linkedlist with your template type as weatherstats.
Your error also states that it cannot convert the weatherstats type.
So the question is: Are you Overloading << for the weatherstats class ?
Unfortunately, you haven't posted the code for this class, so we can't go any further than this. Edit: Code has been posted - still no evidence of overloading
(Also I think Baget makes a good point about the direction of your stream operator later on)
EDIT2: How should you call a function? Is it &classname::function or object.function()?

Answer 2

isn't stream >> obj.value; need to be stream<<obj.value;
it is OUTPUT stream not INPUT