Reading input from text file to array in c++

问题

Alright, be gentle, since I'm very much a novice to programming. So far I've only studied C++ and I'm running Visual Studio 2010 as my compiler. For this program, I'm trying to read from a text input file and write the information to a set of three arrays. One array will handle a list of names, and the other two are for hours worked and hourly pay rate, respectively. I will use the latter two to calculate a set of earnings and output the whole thing to another text file as a report. My problem, however, is with acquiring input for the first array. The input file I'm using has text arranged like this:

J. Doe* 35 12.50 J. Dawn* 20 10.00 .........

The names are trailed by asterisks since I'm trying to use ifstream getline to acquire the names with the asterisks acting as delimiters, and writing the following two numbers into the other two arrays. The latter two values are separated by whitespaces, so I don't think they'll cause any problems. I'm sure there are other errors that need handling but I need to work through the first error before I can start debugging the rest.

My problem occurs with the line where I call inFile.getline, since I get the following error: error C2664: 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::getline(_Elem *,std::streamsize,_Elem)' : cannot convert parameter 1 from 'std::string' to 'char *'.

From what I've read elsewhere, (I think) the problem stems from trying to write a string to a char array, which won't work since they are of different data types. I'm not sure if other feasible methods exist for acquiring the names since I need the delimiter to separate the names from the numerical values. Any advice on how to resolve this issue would be much appreciated.

Here is the source I've written:

#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
using namespace std;

const int EMP_NUM = 5;
const int BASE_HOURS = 40;
const char N_SIZE = 8;

int main()
{
 int i;
 double rEarnings, oEarnings, tEarnings,
 trEarnings, toEarnings, ttEarnings;
 ifstream inFile;
 ofstream outFile;
 inFile.open("records.txt");
 outFile.open("report.txt");

 outFile << setprecision(2) << showpoint << fixed;

 outFile << setw(50) << "Payroll Report" << "\n\n";
 outFile << "EMPLOYEE NAME" << setw(25) << "REGULAR EARNINGS" << setw(25) << "OVERTIME EARNINGS" << setw(25) << "TOTAL EARNINGS" << endl;

 string nameAr[EMP_NUM];
 int hoursAr[EMP_NUM];
 double hrateAr[EMP_NUM];

 for (int i = 0; i < EMP_NUM; i++) // Get input from our input file.
 {
  inFile.getline(nameAr[i], EMP_NUM, "*");
  inFile >> hoursAr[i] >> hrateAr[i];
 }

 for (int i = 0; i < EMP_NUM; i++) // Make the calculations to be sent to our report.
 {
  char nameAr[N_SIZE];
  int hoursAr[N_SIZE];
  double hrateAr[N_SIZE];

  if (hoursAr[i] > 40) // For employees with overtime hours.
  {
  // double rEarnings, double oEarnings, double tEarnings,
  // double trEarnings, double toEarnings, double ttEarnings;
  // rEarnings = 0, oEarnings = 0, tEarnings = 0,
  // trEarnings = 0, toEarnings = 0, ttEarnings = 0;

   rEarnings = BASE_HOURS * hrateAr[i];
   oEarnings = (hoursAr[i] - BASE_HOURS) * hrateAr[i] * 1.5;
   tEarnings = rEarnings + oEarnings;
   trEarnings += rEarnings;
   toEarnings += oEarnings;
   ttEarnings += tEarnings;
   outFile << left << nameAr[i];
   // << setw(25) << right << rEarnings << setw(25) << right << oEarnings << setw(25) << right << tEarnings << endl;

  } 
  else // For employees without overtime hours.
  {
  // double rEarnings, double oEarnings, double tEarnings,
  // double trEarnings, double toEarnings, double ttEarnings;
  // rEarnings = 0, oEarnings = 0, tEarnings = 0,
  // trEarnings = 0, toEarnings = 0, ttEarnings = 0;

   rEarnings = hoursAr[i] * hrateAr[i];
   oEarnings = 0;
   tEarnings = rEarnings + oEarnings;
   trEarnings += rEarnings;
   toEarnings += oEarnings;
   ttEarnings += tEarnings;
   outFile << left << nameAr[i]; 
   // << setw(25) << right << rEarnings << setw(25) << right << oEarnings << setw(25) << right << tEarnings << endl;
  }
 }

 outFile << endl << endl;

 outFile << setw(33) << trEarnings << " *" << setw(23) << toEarnings << " *" << setw(23) << ttEarnings << " *\n\n";

 outFile << left << "TOTAL EMPLOYEES" << " " << (i - 1);

 inFile.close(); outFile.close();

 return 0;
}

I've included the entire program to give you an idea of where I plan to go with the coding. Thanks in advance for the help!

回答1:

fstream's getline function has these signatures.

std::istream& getline (char* s, streamsize n );
std::istream& getline (char* s, streamsize n, char delim );

In your code...

string nameAr[EMP_NUM];
// stuff...
inFile.getline(nameAr[i], EMP_NUM, "*");

You are trying to use a std::string where getline wants a char* - you cannot convert from string to a char* like this.

One approach is you can use a character buffer to store the contents of getline, like this.

const int BUFFER_SIZE = 1024;
char buffer[BUFFER_SIZE];
inFile.getline(buffer, BUFFER_SIZE, '*');
// more stuff...

A better solution

I'd recommend using std::getline from <string>, as you can use string types instead of C-strings.

#include <string>

// stuff...
std::getline(inFile, nameAr[i], '*');

edit Links for you since you are learning

std::getline function example
std::getline function description

回答2:

It appears that you have a pointer problem. You are trying to store a pointer to a char array in nameAr[], correct? What you need to do is define nameAr[] as an array of pointers to char arrays so that you can store a pointer to each name in the nameAr[] array.

Try using this for your name array instead of nameAr[].

nameAr = new char*[EMP_NUM];

来源：https://stackoverflow.com/questions/4108811/reading-input-from-text-file-to-array-in-c

标签

c++

arrays

fstream

ifstream

getline