Creating Class from File

Question

I dont quite get the reason why my program prints out weird numbers which I believe it's the address numbers....I'm trying to read the data from a file and then store them in class instances....the file has the id,x,y,z in a line....it has 10 lines, hence i gotta create 10 class instances..would be glad for your help...^^

class planet
{
public:
    int id_planet;
    float x,y,z;
};

void report_planet_properties(planet& P)
{
    cout<<"Planet's ID: "<<P.id_planet<<endl;
    cout<<"Planet's coordinates (x,y,z): ("<<P.x<<","<<P.y<<","<<P.z<<")"<<endl;
}

planet* generate_planet(ifstream& fin)
{
    planet* p = new planet;
    fin >> (*p).id_planet;
    fin >> (*p).x;
    fin >> (*p).y;
    fin >> (*p).z;
    return (p);
}

int main()
{
    planet* the_planets[10];
    int i=0;
    ifstream f_inn ("route.txt");
    if (f_inn.is_open())
    {
        f_inn >> i;
        for(int j=0;j<i;j++)
        {
            the_planets[j]=generate_planet(f_inn);
            report_planet_properties(*the_planets[i]);
            delete the_planets[j];
        }
        f_inn.close();
    }
    else cout << "Unable to open file";
}

sorry.... the line of code "f_inn >> i" it's because the 1st line in the file shows the number of class tht i need to create... — Amos Chew, Oct 19 '13 at 11:07

PhillipD · Answer 1 · 2013-10-19T12:12:48.930

I don't understand some parts of your code (e.g. why you create new instances of planet inside generate_planet) but I am not an experienced C++ programmer. However, I modified your code and found this one to work:

#include <iostream>
#include <fstream>

using namespace std;

class planet
{
private:
    int id_planet;
    float x,y,z;
public:
    void generate_planet(ifstream& fin);
    void report_planet_properties();
};

void planet::report_planet_properties() {
    cout << "\nPlanet's ID: " << id_planet << endl;
    cout << "\nPlanet's coordinates (x,y,z): ("<< x <<","<< y <<","<< z<<")"<<endl; 
}

void planet::generate_planet(ifstream& fin) {

fin >> id_planet;
fin >> x;
fin >> y;
fin >> z;
} 

int main() {

planet the_planets[10];
int i=0;
ifstream f_inn("route.txt");
if (f_inn.is_open())
{
    f_inn >> i;
    for(int j=0;j<i;j++)
    {
        the_planets[j].generate_planet(f_inn);
        the_planets[j].report_planet_properties();
    }
    f_inn.close();
}
else cout << "Unable to open file\n";
return 0;
}

with route.txt:

gives:

Planet's ID: 1

Planet's coordinates (x,y,z): (4,5,6)

Planet's ID: 2

Planet's coordinates (x,y,z): (7,8,9)

As you can see the functions generate_planet() and report_planet_properties() are now methods of the planet class.

Maybe this can help you.

nice...i understood ur concept...got the proper outputs after editing....thank you so much..^^ — Amos Chew, Oct 19 '13 at 12:06
+1 for object oriented refactoring, a step further would be [overloading](http://stackoverflow.com/questions/4421706/operator-overloading) the `>>` operator for the class `Planet` — A4L, Oct 19 '13 at 12:17
hehehe...^^ yeap...i would save both methods for future reference...once again thank you so much guys... — Amos Chew, Oct 19 '13 at 12:28

score 1 · Accepted Answer · answered Oct 19 '13 at 12:13

1

Your code would work if you use the right index for the_planets

 report_planet_properties(*the_planets[i]);

In the above line you have to use your loop variable j not i which is the number of planets in your file.

 report_planet_properties(*the_planets[j]);

answered Oct 19 '13 at 12:13

A4L

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OMG....LOL....i made a careless mistake there.....totally works indeed....thank you...XD i'll save both methods... – Amos Chew Oct 19 '13 at 12:19
@AmosChew, heh you're welcome, but you should definitely go with PhilipD's method since it is object oriented, see my comment on his answer! – A4L Oct 19 '13 at 12:21

Creating Class from File

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