Ruby and duck typing: design by contract impossible?

Question

Method signature in Java:

public List getFilesIn(List directories)

similar one in ruby

def get_fi         


        

Answer 1

While I love static typing when I'm writing Java code, there's no reason that you can't insist upon thoughtful preconditions in Ruby code (or any kind of code for that matter). When I really need to insist upon preconditions for method params (in Ruby), I'm happy to write a condition that could throw a runtime exception to warn of programmer errors. I even give myself a semblance of static typing by writing:

def get_files_in(directories)
   unless File.directory? directories
      raise ArgumentError, "directories should be a file directory, you bozo :)"
   end
   # rest of my block
end

It doesn't seem to me that the language prevents you from doing design-by-contract. Rather, it seems to me that this is up to the developers.

(BTW, "bozo" refers to yours truly :)