Question

I’ve spent almost 4 hours trying to get past this issue…

I have a text file with over 100 rows. Each row has 4 values separated by commas. I want to be able to extract each value and save it into a variable (v1…v4).

I have used a for loop, as I won’t be reading the entire contents of the file. I’m just trying to get 1 working for now.

So far, I have managed to read a single row. I just need to break the row up now. This is for my Uni assignment, and I am not allowed to use any boost or tokeniser classes. Just getline and other basic commands.

I have this code:

// Read contents from books.txt file
ifstream theFile("fileName.txt");
string v1, v2, v3, v4, line;

for (int i = 0; i < 1; i++) {
    getline(theFile, line, '\n');
    cout << line << endl;  // This part works fine
    getline(line, v1, ",");  // Error here
    cout << v1 << endl;
    getline(line, v2, ",");  // Error here
    cout << v2 << endl;
    getline(line, v3, ",");  // Error here
    cout << v3 << endl;
    getline(line, v4, '\n');  // Error here
    cout << v4 << endl;
}

theFile.close();

The error I get is – error: no matching function for call to ‘getline(std::string&, std::string&, const char [2])

How can I fix this?

Answer 1

The delimiter for getline is a character. You have used double-quote marks "," which represent a string (hence why the compiler error indicates that you’ve used char[2] – string literals contain an additional ‘nul’ character).

Single character values are represented using single quotes instead:

getline(myFile, v1, ',');

edit – I’ve just noticed you’re passing a string as the first parameter, which getline doesn’t support (it won’t let you retrieve tokens directly from a string). You probably wanted to stuff the string into a stringstream instead

#include <sstream>

// etc ...

std::string csv = "the,cat,sat,on,the,mat";
std::istringstream buffer( csv );
std::string token;

while( std::getline( buffer, token, ',' ) )
{
    std::cout << token << std::endl;
}