c++ std::fstream. How do I read a number at the start of the line (a float or an int), and then skip to the next? Using named variables so no loop

Question

I have a text file in the following format:

100 #gravity
5000 #power
30 #fulcrum

I want to assign these values to named variables, like so:

void Game::reloadAttributes()
{
    float test1, test2, test3;
    
    string line;
    std::fstream file;
    file.open("attribs.txt");

    if (file.is_open()) {                

        cin >> test1;
        file.ignore(50, '\n');

        cin >> test2;
        file.ignore(50, '\n');

        cin >> test3;
        file.ignore(50, '\n');

        file.close();
    } 
    else
    {
        cout << "\n****Couldn't open file!!****\n" << endl;
    }

    cout << ">>>> " << test1 << ", " << test2 << ", " << test3 << endl;
}

Of course, these aren't destined for the local test variables, but in fields belonging to the Game class, just using these to test its reading correctly. The program just hangs at cin >> test1. Ive tried using getLine(file, line) just beforehand, that didnt work. What am I doing wrong? Cheers

score 1 · Answer 1 · answered Mar 18 '22 at 15:04

1

You're using cin instead of file for your input lines.

Instead of cin >> test1;, do file >> test1;. Then it should work fine.

answered Mar 18 '22 at 15:04

Jan

848
7
17

score 0 · Accepted Answer · answered Mar 18 '22 at 15:01

0

An object of type istream (in this case cin) takes user input. So of course the program will wait for you to input a value and then store it inside test1, test2, and test3 respectively.

To fix your issue, just replace cin with file as such:

file >> test1;
file.ignore(50, '\n');

file >> test2;
file.ignore(50, '\n');

file >> test3;
file.ignore(50, '\n');

file.close();

Output:

>>>> 100, 5000, 30

answered Mar 18 '22 at 15:01

The Coding Fox

1,488
1
4
18

"*An object of type `istream` ... takes user input*" - that is misleading. Not all `istream`s take in *user* input. Only the `std::cin` stream specifically does. – Remy Lebeau Mar 18 '22 at 18:11

c++ std::fstream. How do I read a number at the start of the line (a float or an int), and then skip to the next? Using named variables so no loop

2 Answers2

Output: