attempting to reference a deleted function - c++

Question

I'm trying to learn about the fstream class and I'm having some trouble. I created a couple of txt files, one with a joke and the other with a punchline (joke.txt) and (punchline.txt) just for the sake of reading in and displaying content. I ask the user for the file name and if found it should open it up, clear the flags then read the content in. but I cant even test what it reads in because I'm currently getting errors regarding a deleted function but I don't know what that means
error 1:
"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
the second error is the exact same but for the 2nd function (displayLastLine())
and error 3:
Error 1 error C2280: 'std::basic_ifstream<char,std::char_traits<char>>::basic_ifstream(const std::basic_ifstream<char,std::char_traits<char>> &)' : attempting to reference a deleted function
and here's my code:
#include "stdafx.h"
#include <string>
#include <iostream>
#include <fstream>
using namespace std;
void displayAllLines(ifstream joke);
void displayLastLine(ifstream punchline);
int main()
{
string fileName1, fileName2;
ifstream jokeFile, punchlineFile;
// Desribe the assigned project to the User
cout << "This program will print a joke and its punch line.\n\n";
cout << "Enter the name of the joke file (ex. joke.txt): ";
cin >> fileName1;
jokeFile.open(fileName1.data());
if (!jokeFile)
{
cout << " The file " << fileName1 << " could not be opened." << endl;
}
else
{
cout << "Enter name of punch line file (ex. punchline.txt): ";
cin >> fileName2;
punchlineFile.open(fileName2.data());
if (!punchlineFile)
{
cout << " The file " << fileName2 << " could not be opened." << endl;
jokeFile.close();
}
else
{
cout << endl << endl;
displayAllLines(jokeFile);
displayLastLine(punchlineFile);
cout << endl;
jokeFile.close();
punchlineFile.close();
}
}
// This prevents the Console Window from closing during debug mode
cin.ignore(cin.rdbuf()->in_avail());
cout << "\nPress only the 'Enter' key to exit program: ";
cin.get();
return 0;
}
void displayAllLines(ifstream joke)
{
joke.clear();
joke.seekg(0L, ios::beg);
string jokeString;
getline(joke, jokeString);
while (!joke.fail())
{
cout << jokeString << endl;
}
}
void displayLastLine(ifstream punchline)
{
punchline.clear();
punchline.seekg(0L, ios::end);
string punchString;
getline(punchline, punchString);
while (!punchline.fail())
{
cout << punchString << endl;
}
}

Answer 1

You do call a deleted function, being the copy constructor of the class std::ifstream.
If you take a look at the reference you notice, that the copy constructor is not allowed.
so instead of using:
void displayAllLines(ifstream joke);
void displayLastLine(ifstream punchline);
you should work with calls by reference:
void displayAllLines(ifstream& joke);
void displayLastLine(ifstream& punchline);
Using a reference will behave just like calling the method with a copy, but in fact you are operating on the original object instead of a new copy-constructed object. Keep that in mind for further use of the call by reference.