How can I alternate taking one line of data from a file and one integer?

Question

I am trying to extract data from one file and add each line to alternating lines. Example .txt file:

123 Main
500
555 Acorn
1500
23 Smithville
1540

I have an address array to hold the strings and amountDue array to hold integers. Ideally address[0] holds "123 Main" and amountDue[0] holds 500, etc.

The function I have made for this uses getline to get the string and works for the first loop but the inputFile >> amountDue[0] recieves more than the 500 integer. It takes 500 555, then the next getline takes "Acorn" and the next inputFile >> amountDue[1] takes 1500 23.

void loadArrays(string address[], double amountDue[], const int SIZE)
{
//Open file for data laoding
ifstream inputFile;
inputFile.open("Prog3Input.txt");

for (int i = 0; i < SIZE; i++)
{
    getline(inputFile,address[i]);
    inputFile >> amounDue[i];
}
}

I expected: string address[0] is "123 Main"
int amountDue[0] is 500
address[1] is "555 Acorn"
amountDue[1] is 1500
ETC.

I am getting: address[0] is "123 Main"
amountDue[0] is 500 555
address[1] is "Acorn"
amountDue[1] is 1500 23
ETC

Answer 1

the inputFile >> amountDue[0] recieves more than the 500 integer. It takes 500 555

No, it doesn't. That it not how the operator>> works. It stops reading on the first character that does not fit in an integer, which includes whitespace and line breaks.

So, it reads just the 500, then the next getline() finishes the integer line and returns a blank string, then the next >> reads the number of the address line, then the next getline() finishes the address line. And so on.

That said, your code is not accounting for the line breaks after each integer. You need to update your code in one of the following ways:

• use std::istream::ignore() to skip the rest of the line until the line break.

  #include <string>
  #include <fstream>
  #include <limits>
  
  void loadArrays(std::string address[], double amountDue[], const int SIZE)
  {
      //Open file for data loading
      std::ifstream inputFile("Prog3Input.txt");
  
      for (int i = 0; i < SIZE; i++)
      {
          std::getline(inputFile, address[i]);
          inputFile >> amountDue[i];
          inputFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
      }
  }
  

  Live demo

• always use std::getline() to read each line, and then use std::istringstream to parse the integers.

  #include <string>
  #include <fstream>
  #include <sstream>
  
  void loadArrays(std::string address[], double amountDue[], const int SIZE)
  {
      //Open file for data loading 
      std::ifstream inputFile("Prog3Input.txt");
      std::string line;
  
      for (int i = 0; i < SIZE; i++)
      {
          std::getline(inputFile, address[i]);
          std::getline(inputFile, line);
          std::istringstream(line) >> amountDue[i];
      }
  }
  

  Live demo