How to make object instance a hash key in Ruby?

Question

I have a class Foo with a few member variables. When all values in two instances of the class are equal I want the objects to be \'equal\'. I\'d then like these objects to be

Answer 1

Add a method called 'hash' to your class:

class Foo
  def hash
    return whatever_munge_of_instance_variables_you_like
  end
end

This will work the way you requested and won't generate different hash keys for different, but identical, objects.