[error in compilation .its is a deleted function] - c++

Question

I am getting below error:
2 IntelliSense: function "std::basic_ifstream<_Elem, _Traits>::basic_ifstream(const std::basic_ifstream<_Elem, _Traits>::_Myt &) [with _Elem=char, _Traits=std::char_traits<char>]" (declared at line 818 of "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\include\fstream") cannot be referenced -- it is a deleted function c:\Users\varunk\Documents\Visual Studio 2013\Projects\hashmaptest\hashmaptest\hashmaptest.cpp 12 48 hashmaptest
Here is my code which is showing the error:
// hashmaptest.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
Init ini;
ifstream file("D:/test.txt", ios::in);
ini.filterng_three_addId_on_location_and_time(file);
file.close();
// Node shoom = Node ("ram", 14);
// myMap.insert(std::make_pair(Node("abc",18), 16));
return 0;
}
#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
#include "stdafx.h"
#include <iostream>
#include <unordered_map>
#include <string>
#include<vector>
#include<string>
#include <bitset>
#include <utility>
#include <fstream>
using namespace std;
class FilterKeys
{
public:
FilterKeys(string a, int b)
{
name = a;
time = b;
}
string name;
int time;
};
class HashKey
{
public:
size_t operator() (FilterKeys const& key) const
{
return std::hash<std::string>()(key.name) ^
(std::hash<int>()(key.time) << 1);
}
};
class EqualTo
{
public :
bool operator()(const FilterKeys& lhs, const FilterKeys& rhs) const
{
return lhs.name == rhs.name && lhs.time == rhs.time;
}
};
class Init {
unordered_multimap<FilterKeys, int, HashKey, EqualTo> _myMap;
public:
void filterng_three_addId_on_location_and_time(ifstream file)
{
string location;
int time, addId;
if (!file)
cerr << "Cant open " << endl;
while (file >> location >> time >> addId)
{
if (_myMap.count(FilterKeys(location, time)) < 3)
_myMap.insert(std::make_pair(FilterKeys(location, time), addId));
}
}
unordered_multimap<FilterKeys, int, HashKey, EqualTo> getHashMap()
{
return _myMap;
}
};

Answer 1

The error is telling you that you can't call the copy constructor of ifstream - it doesn't have one.
You need to change:
void filterng_three_addId_on_location_and_time(ifstream file)
to
void filterng_three_addId_on_location_and_time(ifstream& file)
This will mean that you pass a reference to the file object (rather than a copy). You need to be aware that passing a reference means that changes you make in the called function will be seen in main.
In other cases, you may want to pass a reference, but forbid the called function from making changes to the object. In that case you would write:
void filterng_three_addId_on_location_and_time(const ifstream& file)
(a reference to const). That won't work here, because all the input functions modify the ifstream object, so you would get a compiler error when you called them.