CODEWITHSUNDEEP
c++file-iogetline
AlphaOmegaStrife
AlphaOmegaStrife

Reputation: 83

File I/O Code Not Reading Correctly C++

void createVideoList(ifstream& ifile, Video videoArray[])
{
string title;
string star1;
string star2;
string producer;
string director;
string productionCo;
int inStock;
int count = 0;
Video newVideo;
getline(ifile, title);
while (ifile)
{
    ifile >> inStock;
    getline(ifile, title);
    getline(ifile, star1);
    getline(ifile, star2);
    getline(ifile, producer);
    getline(ifile, director);
    getline(ifile, productionCo);
    videoArray[count] = Video(inStock, title, star1, star2, producer, director, productionCo);
    count++;
}
}

This is my code for a programming assignment. It will read in from a .txt file and is going to place the information into an array of a class I created.

The .txt is formatted like so:

3 (amount in stock)
Movie Title
Movie Star1
Movie Star2
Movie Producer
Movie Director
Movie ProductionCo

However, my code does not seem to be gathering the data correctly into the videoArray. I just switched over from Java so my C++ syntax is a little rusty. Am I using getline correctly? If I try to output one of the indexes, it has nothing in any of the variables. Thanks in advance!

Upvotes: 1

Views: 410

Answers (1)

Robᵩ
Robᵩ

Reputation: 168876

Video newVideo;
getline(ifile, title);
while (ifile)
{
    ifile >> inStock;
    getline(ifile, title);
    getline(ifile, star1);
    ...

It is mostly correct, but there are a few problems:

  • The first getline, the one outside of the loop, shouldn't be there. What is it supposed to read?
  • The loop test isn't exactly correct -- what happens if the last record is only partially present?
  • You have to be careful when you mix >> with getline. The >> doesn't read in the remainder of the first line -- specifically, it leaves the \n in the input stream. Use std::getline or istream::ignore to remove the pending end-of-line.
  • You are better of using a std::vector instead of an array, if the homework assignment allows it.

Try:

while (ifile >> inStock && getline(ifile, temporary_string) &&
       getline(ifile, title) &&
       getline(ifile, star1) &&
       ...
       getline(ifile, productionCo) )
{
  videoVector.push_back(Video(inStock, title, ..., productionCo_));

  // Or, as a less worthy alternative, 
  //  videoArray[count] = Video(inStock, title, star1, star2, producer, director, productionCo);
  //  count++;
}

As a demonstration of the language features that you will learn in the coming weeks, here is one implementation of your program using modern C++ features:

std::istream&
operator>>(std::istream& is, Video& v)
{
  is >> v.inStock;
  is.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  std::getline(is, v.title);
  std::getline(is, v.star1);
  std::getline(is, v.star2);
  std::getline(is, v.producer);
  std::getline(is, v.director);
  std::getline(is, v.productionCo);
  return is;
}
std::vector<Video> void createVideoList(std::istream& ifile)
{
  std::vector<Video> result;
  std::istream_iterator<Video> begin(ifile), end;
  std::copy(begin, end, std::back_inserter(result));
  return result;
}

Upvotes: 4

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