c++ ifstream file is open but fails

im trying to parse a file. however, the ifstream object keeps failing. in my parsing header file i have this:

class ParseDFA {
public:
  bool stop_program = false;
  std::ifstream dfa_file;
  ParseDFA(std::string parse_filename);
};

in my parsing cpp file i have this:

ParseDFA::ParseDFA(std::string parse_filename) {
  dfa_file.open(parse_filename, std::ifstream::in);

  if (dfa_file.fail()) {
    stop_program = true;
  }
}

and in my main.cpp file i have this:

std::string filename = "no000.dfa";
ParseDFA *dfa_file = new ParseDFA(filename);
if (dfa_file->stop_program) {
  std::cout << "Error opening file." << std::endl;
  return 0;
}

my output:

Error opening file.

I know the file is open because in my parsing cpp file, i changed dfa_file.fail() to !dfa_file.is_open() and it stopped giving me that error. so what am i doing wrong?

EDIT: I was able to fix the problem by putting the file's full path in variable filename. so like in my main.cpp file i have

std::string filename = "/Users/myname/Documents/DFA/no000.dfa";