How do I iterate over cin line by line in C++?

Question

I want to iterate over std::cin, line by line, addressing each line as a std::string. Which is better:

string line;
while (getline         


        

Answer 1

What I have (written as an exercise, but perhaps turns out useful one day), is LineInputIterator:

#ifndef UB_LINEINPUT_ITERATOR_H
#define UB_LINEINPUT_ITERATOR_H

#include 
#include 
#include 
#include 

namespace ub {

template 
class LineInputIterator :
    public std::iterator
{
public:
    typedef typename StringT::value_type char_type;
    typedef typename StringT::traits_type traits_type;
    typedef std::basic_istream istream_type;

    LineInputIterator(): is(0) {}
    LineInputIterator(istream_type& is): is(&is) {}
    const StringT& operator*() const { return value; }
    const StringT* operator->() const { return &value; }
    LineInputIterator& operator++()
    {
        assert(is != NULL);
        if (is && !getline(*is, value)) {
            is = NULL;
        }
        return *this;
    }
    LineInputIterator operator++(int)
    {
        LineInputIterator prev(*this);
        ++*this;
        return prev;
    }
    bool operator!=(const LineInputIterator& other) const
    {
        return is != other.is;
    }
    bool operator==(const LineInputIterator& other) const
    {
        return !(*this != other);
    }
private:
    istream_type* is;
    StringT value;
};

} // end ub
#endif

So your loop could be replaced with an algorithm (another recommended practice in C++):

for_each(LineInputIterator<>(cin), LineInputIterator<>(), do_stuff);

Perhaps a common task is to store every line in a container:

vector lines((LineInputIterator<>(stream)), LineInputIterator<>());