Reading from a file using getline c++

Question

I have a file that looks like:

Sister Act
Whoopi GoldBerg
Maggie Smith
Schwartz
Ardolino
Touch Stone Pictures
14

I am having trouble reading in the information and saving it to an object. I am not getting any error but I can not get program to read the information correctly.

My question is can anyone tell me what I need to change to make the my program read the file correctly.

Also each row can have multiple words and whitespace except for the integer in row 7.

string title, starName1, 
    starName2, producer, 
    director, prodCo;
int numCopies;
ifstream videoFile("videoDat.txt");

if (videoFile.is_open()) {
    getline(videoFile, title);
    getline(videoFile, starName1);
    getline(videoFile, starName2);
    getline(videoFile, producer);
    getline(videoFile, director);
    getline(videoFile, prodCo);
    //getline(videoFile, numCopies); //compiler error

    while (videoFile >> title >> starName1 >> starName2 >> producer >> director >> prodCo >> numCopies) {
        //be able to do stuff with variables individually
    }
}

I was thinking i needed to do something like:

    while (getline(videoFile, title) && getline(videoFile, starName1) && getline(videoFile, starName2) 
        && getline(videoFile, producer) && getline(videoFile, director) && getline(videoFile, prodCo) && videoFile >> numCopies) {
        //be able to do stuff with variables individually
    }

Please provide MCVE, it's hard to reason about compilation and correctness errors when there are a lot of user-defined types in the snippet. — yeputons
– yeputons, Commented Feb 21, 2017 at 3:58
I tried to edit leaving only code that is giving me problems with no user-defined types. — Asuu
– Asuu, Commented Feb 21, 2017 at 4:07

Germán Diago · Accepted Answer · 2017-02-21 04:18:03Z

2

getline(videoFile, numCopies); //numCopies should not be an int, but a str.

numCopies is an int. Do this:

 string numCopiesStr;

 getline(videoFile, numCopiesStr);
 int numCopies = std::stoi(numCopiesStr);

That should work.

Another way, but the error handling gets trickier, is to use std::cin:

 std::cin >> numCopies;

That will read the int into the numCopies variable but will stop there exactly, after that, without getting the full line.

You cannot read strings separated by spaces with operator>>, it will stop at the first space. You need getline.

My recommendation is that you use a string numCopiesStr and convert to int inside the loop for each iteration.

Another solution (since C++14) is to use the std::quoted modifier if you can change the format of the input file (add quotes to Sister Act, for example "Sister Act", etc). In that case you could use an int directly for numCopies and do this, as long as you quote every string that is not numbers:

while (std::quoted(videoFile) >> std::quoted(title) ... >> numCopies) {
}

See how to use std::quoted here: http://en.cppreference.com/w/cpp/io/manip/quoted

Ah, and keep your cppreference.com always close to you, it can help a lot ;)

edited Feb 21, 2017 at 4:18

answered Feb 21, 2017 at 4:11

Germán Diago

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1 Comment

Asuu Over a year ago

This solved my problem with some trial and error. Atleast put me on the right track, Thank You.

Community · Accepted Answer · 2017-05-23 12:24:59Z

0

The default behavior of getline(...) is to read from the input stream and store it in a string. Check here. http://en.cppreference.com/w/cpp/string/basic_string/getline

Thus, you will have to do any of the string to int conversion techniques to read using getline and convert it as int.

Suggestion : For converting from string to int, depending on performance vs accuracy you can check out : boost::coerce or boost::lexical cast or sscanf or stoi. Check : Alternative to boost::lexical_cast

edited May 23, 2017 at 12:24

CommunityBot

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answered Feb 21, 2017 at 8:41

svarghese

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Comments

Asuu · Accepted Answer · 2017-02-21 18:25:51Z

0

I know I have user defined data types here but this is what I did to solve the problem. I read it in as a string in my while loop then converted it to an integer using stoi. Thanks all for the help!

     while (getline(videoFile, title) && getline(videoFile, starName1) 
        && getline(videoFile, starName2) && getline(videoFile, producer) 
        && getline(videoFile, director) && getline(videoFile, prodCo) 
        && getline(videoFile, numCopiesStr)) {
        tempVideo.setVideos(title, starName1, starName2, producer, director, prodCo, stoi(numCopiesStr));
        videos.addNodeToTail(tempVideo);
    }
}

answered Feb 21, 2017 at 18:25

Asuu

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