How to read a separate line from textfile for different objects? - c++

Question

I have two rectangles objects which I'm trying to read different lines in a textfile with readcood() however when I run this I get the same line from the text file.
#include<iostream>
#include<fstream>
using namespace std;
class rect{
int xcood[3],ycood[3],x1,x2,x3,x4,y1,y2,y3,y4;
public:
void readcood()
{
char dummy;
ifstream myfile;
myfile.open("coordinates.txt");
for(int i=0;i<4;i++)
{
myfile>>xcood[i]>>dummy>>ycood[i];
}
}
void printcood()
{
for(int i=0;i<4;i++)
{
cout<<xcood[i]<<"\t"<<ycood[i]<<endl;
}
}
};
int main()
{
char dummy;
string coordinates;
rect rectangle1,rectangle2;
rectangle1.readcood();
rectangle2.readcood();
rectangle1.printcood();
rectangle2.printcood();
}

Answer 1

It's because you open the file in the function. When the function returns the file-stream object will be destructed and all you've done will be lost.
You could open it in the main function and pass it (by reference) to the read function.
Another solution is to add an open function to your rect class, that opens the file, and have the file stream being a member of the class.
However the solution I would recommend is to make your own overloaded input function, that takes a rect object and reads into that. Something like
class rect
{
public:
...
friend std::istream& operator>>(std::istream& is, rect& r)
{
char dummy;
for (int i = 0; i < 3; ++i)
is >> r.xcood[i] >> dummy >> r.ycood[i];
return is;
}
...
};
Then you can simply do e.g.
std::ifstream file("some/path/file");
rect r1, r2;
file >> r1 >> r2;