string_array[i] = my_str?

**avgprogamerjoe** · 08-20-2007

Hey guys I have been trying to get make a simple program to store all of the names, in a file, in an array of strings. But I'm not quite sure how. I got to this till I couldn't figure it out any further. Is the code below on the right track, and if so, why am I getting the error?

Code:

// reading a text file
#include <iostream>    //import
#include <fstream>
#include <string>
using namespace std;    //namespace std

char names[25][10];    //make an array of 25 strings, 10 chars long
int i = 0;    

int main () {
  string line;        //initiate a string


  ofstream people ("example.txt");         //open file

  people<< "Joe \nBob \nBill";       //write names
  people.close();          ///close file, so it can be opened in read mode

  ifstream myfile ("example.txt");      //read file

  if (myfile.is_open())        //check if file is there

  {

    while (! myfile.eof() )      // set up loop

    {

      getline (myfile,line);      //read line
      names[i] = line;         //put string in array<!--gets error-->
      i++;                           //sets array position

    }
    i = 0;

    while(i < 3)
    {
        cout<< names[i];           //reads array of strings
        i++;
    }

    myfile.close();       //closes file

  }

  else cout << "Unable to open file";       //If file is not there

  return 0;
}

Which gives the error

Code:

main.cpp: In function `int main()':
main.cpp:30: error: incompatible types in assignment of `std::string' to `char*[50]'
main.cpp:49:2: warning: no newline at end of file
Process terminated with status 1 (0 minutes, 0 seconds)

Why is it not allowing me to enter the string into the array?

Thanks for any help,

Joe

**hk_mp5kpdw** · 08-20-2007

You can't assign a std::string object to a char array, they are completely different types. You could strcpy the contents of the std::string into the char array like so:

Code:

strcpy(names[i],line.c_str());

However you should prefer the use of one of the handy STL containers to store your strings into such as a vector. They can grow and shrink as necessary so you aren't limited to a hard-coded value like 25.

Code:

#include <vector>
#include <algorithm> // For the "copy" STL function
#include <iterator> // For "ostream_iterator"
...

vector<string> names;

...

if (myfile.is_open())        //check if file is there
{
    // Read the contents of the file into the string vector. //
    while ( getline(myfile,line) )
        names.push_back(line);

    // Output contents of vector using cout. //
    copy(names.begin(),names.end(),ostream_iterator<string>(cout,"\n"));

    myfile.close();       //closes file

}

**CodeMonkey** · 08-20-2007

And to point out an important design difference between hk_mp5kpdw's code and yours...

Code:

while (! myfile.eof() )      // set up loop

    {

      getline (myfile,line);      //read line

That set up is going to set you up for corrupted data. See hk_mp5kpdw's

Code:

while ( getline(myfile,line) )
        names.push_back(line);

You put the read-in code as the conditional.

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