Doesn't stop for user input

[Nathan Reynolds]

I have put this code in int main() and it worked fine but in a separate function is just runs straight thru non stop for users input ? I got this code from a already asked question .. just debugged it and it says theirs an error on line 4 "ofstream f;"

void makefile(){

    ofstream f;
    string filename;

    cout << "Please enter a file name to write: ";
    getline( cin, filename );

    f.open( filename.c_str() );
    f << "Hello world!\n";
    f.close();

     cout << "Success\n";

}

[Duthomhas]

Chances are you have, somewhere else in your program, something like

cin >> x;

Right?


What no one teaches new programmers in C++ (and C) is that you should always read user input as a whole-line string, then convert that string to what you want.

Yes, I know that cin is an istream, with all kinds of nice, overloaded extraction functions, but you shouldn't use them. Use an istringstream for that.

The reason is fairly simple: The user will always press Enter at the end of every input!

I find useful functions to be... well, useful. Here's a full-fledged example to get started:

#include <iostream>
#include <sstream>
#include <string>

int get_an_integer( std::istream& ins )
{
  // Get an entire line input from the user
  std::string s;
  std::getline( ins, s );

  // Get rid of any trailing whitespace
  s.erase( s.find_last_not_of( " \t\r\n\f\v" ) + 1 );

  // Try to convert it to the object of our desire (an int)
  std::istringstream ss( s );
  int result;
  ss >> result;

  // Check for success or failure.
  if (!ss.eof()) cin.setstate( std::ios::failbit );

  // Return the (potentially invalid) result
  return result;
}

int main()
{
  using namespace std;

  int age;
  string name;

  cout << "How old are you? ";
  age = get_an_integer( cin );

  cout << "What is your name? ";
  getline( cin, name );

You can easily add error processing to that:

int main()
{
  using namespace std;

  int age;
  string name;

  cout << "How old are you? ";
  while (true)
  {
    age = get_an_integer( cin );
    if (!cin or (age < 0))
    {
      cin.clear();
      cout << "Your age must be a whole number, like 24 or 7. How old are you? ";
    }
    else break;
  }

  cout << "What is your name? ";
  while (true)
  {
    getline( cin, name );
    name.erase( name.find_last_not_of( " \t\n\r\f\v" ) + 1 );
    if (name.empty())
    {
      cout << "You must have a name. What is it? ";
    }
    else break;
  }

  if (age < 3) 
    cout << "Hey, " << name << ", you're a good reader!\n";
  else
    cout << name << ", " << age << " years old, earns 7 EP.\n";

And now you know the ugly truth. Input is difficult.

Sorry. Hope this helps.

[Nathan Reynolds]

Big thanks Duoas had no idea .

[Duthomhas]

I forgot to respond to the issue about line 4. Did you #include <fstream> ?