Programming Forums - Deriving a new ifstream class

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Deriving a new ifstream class

I would like to derive a new ifstream class, that would ignore comments in a file (lines that start with a '#' character). For instance:

Input file (f.txt)

#This is a comment

This is not

An example of use

int main(){

  

  string a;

  commentStream cs("f.txt");



  if(!cs) exit(1);

  else{

     while(cs){

        cs >> a;

        cout << a << endl;

     }

  }

  return (0);

}

Expected output

This

is

not

I know I'm suppose to derive a new streambuf and than derive the new stream using this streambuf. But I can't figure out how the new streambuf should look like (which methods should be overridden and what should they do). I think I should override the underflow method but I'm not exactly sure how.

Any help would be welcome.

Re: Deriving a new ifstream class

Why not create a separate read() function in your program that accepts the ifstream object pointer as input. The function can then read a line from the file, if it's a comment ignore it and get the next one, else return the read line.