Multiple use of function that reads from a file

Question

In my program I have function Get_auto(); I want it to do something like this:

void Cook::Get_auto(){  
ifstream ifile;
ifile.open("sourcek.txt");
char choice;
ifile >> choice;
switch (choice)
{
case '0': lvl = 0;
    break;
case '1': lvl = 1;
    break;
case '2': lvl = 2;
    break;
case '3': lvl = 3;
    break;
case '4': lvl = 4;
    break;
}
}

The problem is that I want to use the Get_auto function multiple times, each time loading the data below the last used part of a file. How should I do this?

Answer 1

Move the ifstream to the class as its private field. Then, create a method Cook::open, where you open the ifstream. In Cook::Get_auto only use the >> operator. Call the open method before you call the Get_auto method for the first time.

Something like this: (assuming its a C++ code, this will be in the header file)

private:
    ifstream ifile;

public:
    void open();
    void Get_auto();

and this will be in the source file:

void Cook::open() {
    ifile.open("sourcek.txt");
}

void Cook::Get_auto(){  
    char choice;
    ifile >> choice;
    switch (choice)
    {
    case '0': lvl = 0;
        break;
    case '1': lvl = 1;
        break;
    case '2': lvl = 2;
        break;
    case '3': lvl = 3;
        break;
    case '4': lvl = 4;
        break;
    }
}

It would be wise also to add some checking whether ifile is open and whether you can read from it.