Simon Willison’s Weblog

How not to use OOP

5th December 2003

Via Hans Nowak, Understanding Object Oriented Programming, or how to turn 19 lines of easily maintained code in to an OO monstrosity spanning 7 class files. This is not the way to make code more maintainable. For comparison, here’s how I would implement a solution to the same problem in Python, assuming the availability of an equivalent function to Java’s System.getProperty("os.name") (os.name is similar but inappropriate for this example):

MESSAGES = (
  ('SunOS', 'Linux'), 'This is a UNIX box and therefore good.'),
  ('Windows NT', Windows 95'), 'This is a Windows box and therefore bad.),
)
DEFAULT_MESSAGE = 'This is not a box.'

def get_os():
    name = System.getProperty("os.name")
    for names, message in MESSAGES:
        if name in names:
            return message
    return DEFAULT_MESSAGE

if __name__ == "__main__":
    print get_os()	

In my book, smart data-driven programming beats over-engineered class-based programming any day of the week.