How to write class' objects to as a text file

[student78]

Hello,

I need to a simple example for writing class' objects to a text file using fstream , I tried to search the forums and I found binary examples but not for to a text file. Could you help me please ?

Regards

Kevin S.

[weaknessforcats]

You should be able to use the insertion operator<<. fstream knows whether the file is text or binary. All you have to do is get your data into the stream.

[student78]

Here is the my code, is it possible to correct the code ? I recieve related class showit has no member for related letter.

Regards

Kevin S.

#include<iostream>
#include<fstream>
#include <cstdlib>
#include <math.h>
#include <conio.h>
using namespace std;
 
class showit {
      int numberx;
      public:
             void assignx(int a){
                  numberx=a;
                  }
      int xprint(){
          return numberx;
          }
      }k,e,v,i,n;
      int main(){
          k.assignx(1);
          e.assignx(2);
          v.assignx(3);
          i.assignx(4);
          n.assignx(5);
      cout << k.xprint() << endl;
      cout << e.xprint() << endl;
      cout << v.xprint() << endl;
      cout << i.xprint() << endl;
      cout << n.xprint() << endl;
      system("pause");      
}
class filex 
{
      private :
             showit infox;
              void writeToFile()
              {
                  ofstream  yprint("newFile.txt", ios::app);
                  yprint << infox.k << endl;
                  yprint << infox.e << endl;
                  yprint << infox.v << endl;
                  yprint << infox.i << endl;
                  yprint << infox.n << endl;
                  yprint.close();
                  }
}

[weaknessforcats]

OK. I fixed your code.

Let's take this in pieces. Here's the new main():

     int main(){
          showit k,e,v,i,n;
          k.assignx(1);
          e.assignx(2);
          v.assignx(3);
          i.assignx(4);
          n.assignx(5);
 
          filex obj;
                obj.writeToFile(k);
                 obj.writeToFile(e);
                  obj.writeToFile(v);
                  obj.writeToFile(i);
                  obj.writeToFile(n);
 
      cout << k.xprint() << endl;
      cout << e.xprint() << endl;
      cout << v.xprint() << endl;
      cout << i.xprint() << endl;
      cout << n.xprint() << endl;
      system("pause");      
}

The first thing is some objects of type showit are created. These objects are k,e,v,i,n.

Next, the objects are assigned a value.

Next a filex object s created.

Next, each showit object is written to file.

And you are done.

To make this work, the filex class now looks like:

class filex 
{
      private :
             showit infox;
             ofstream theFile;
 
public:
      filex();
      ~filex();
      void writeToFile(showit& arg);
 
};
 
 
filex::filex()
{
    this->theFile.open ("newFile.txt", ios::app);
}
filex::~filex()
{
      this->theFile.close();
}
void filex::writeToFile(showit& arg)
{
                  theFile << arg.xprint() << endl;
 
 }

Here you see the class has a constructor to open the file and a destructor to close the file. Then there is the writeToFile method which writes the showit object passed in as an argument to the file.

So this code:

filex obj;
 
 

has created the filex object and has called the filex constructor which as opened the file.

The filex destructor will be called at the end of the program by the compiler without you needing to code anything.

So, what dot you think?

[student78]

Thank you for your interest but it is not working. When I try to run, I receive following error message.
"filex" undeclared (first use this function)

used code is below as you suggested

#include<iostream>
#include<fstream>
#include <cstdlib>
#include <math.h>
#include <conio.h>
using namespace std;
 
class showit {
      int numberx;
      public:
             void assignx(int a){
                  numberx=a;
                  }
      int xprint(){
          return numberx;
          }
      }k,e,v,i,n;
      int main(){
          showit k,e,v,i,n;
          k.assignx(10);
          e.assignx(20);
          v.assignx(30);
          i.assignx(40);
          n.assignx(50);
 
          filex obj;
                obj.writeToFile(k);
                 obj.writeToFile(e);
                  obj.writeToFile(v);
                  obj.writeToFile(i);
                  obj.writeToFile(n);
 
                  cout << k.xprint() << endl;
                  cout << e.xprint() << endl;
                  cout << v.xprint() << endl;
                  cout << i.xprint() << endl;
                  cout << n.xprint() << endl;
                  system("pause");     
}
 
class filex 
{
      private :
             showit infox;
             ofstream theFile;
 
public:
      filex();
      ~filex();
      void writeToFile(showit& arg);
};
filex::filex()
{
    this->theFile.open ("newFile.txt", ios::app);
}
filex::~filex()
{
      this->theFile.close();
}
void filex::writeToFile(showit& arg)
{
                  theFile << arg.xprint() << endl;
 
 }
 

Regards

Demir

[student78]

if I disable line 26 to 31 the code working but off douse it is not writing any thing.

Regards

Demir

[student78]

I mean that of course:) sorry

[weaknessforcats]

The compiler needs to know about filex before you use it. Therefore, you can't put the filex class after main().

Put the class between the showit class and the start of main().

I did that with your code plus removing k,e,v,i,n from the end of the showit class definition. I compiled the code, and verified that, in fact, it wrote to the disc file just fine.

[student78]

it is worked after move class filex between showit and start of main. I will try to read the file same way.

thank you so much :)

Demir