Reading getline from cin into a stringstream (C++)

Question

So I'm trying to read input like this from the standard input (using cin):

Adam English 85
Charlie Math 76
Erica History 82
Richard Science 90

My goal is to eventually store each data piece in its own cell in a data structure I have created, so basically I want to parse the input so each piece of data is individual. Since each row of input is inputted by the user one at a time, each time I get an entire row of input that I need to parse. Currently I am trying something like this:

stringstream ss;
getline(cin, ss);

string name;
string course;
string grade;
ss >> name >> course >> grade;

The error I am having is that XCode is telling me there's no matching function call to getline which is confusing me. I have included the string library, so I'm guessing the error has to do with using getline to read in from cin to a stringstream? Any help here would be appreciated.

Solution 1

You are almost there, the error is most probably¹ caused because you are trying to call getline with second parameter stringstream, just make a slight modification and store the data within the std::cin in a string first and then used it to initialize a stringstream, from which you can extract the input:

// read input
string input;
getline(cin, input);

// initialize string stream
stringstream ss(input);

// extract input
string name;
string course;
string grade;

ss >> name >> course >> grade;

---

^{1. Assuming you have included:}

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

using namespace std;

Solution 2

You cannot std::getline() a std::stringstream; only a std::string. Read as a string, then use a stringstream to parse it.

struct Student
{
  string   name;
  string   course;
  unsigned grade;
};

vector <Student> students;
string s;
while (getline( cin, s ))
{
  istringstream ss(s);
  Student student;
  if (ss >> student.name >> student.course >> student.grade)
    students.emplace_back( student );
}

Hope this helps.

Solution 3

You can just use cin >> name >> course >> grade; because >> will read until whitespace anyway.

Comments

[Christian Hackl]

Do you realise that your program will only work if name and course do not contain spaces? It will fail for "John Smith English" or "Adam Computer Science"...

[Lightness Races in Orbit]

Adding a line-by-line parsing layer is usually actually a good thing, though.

[Manohar Reddy Poreddy]

this is best answer for me

[Kasper]

"will read until whitespace": it is not accurate. It'll read until the whitespace or tab or end of line

[Yazan Alsalem]

@Kasper tab and end-of-line characters are considered whitespace

[Kasper]

you're right @YazanAlsalem. Specifically: cplusplus.com/reference/istream/istream/operator-free and cplusplus.com/reference/cctype/isspace for detailed info.