oop - Ruby class associations -

i'm having problem creating class association in ruby, since it's dynamic typed language. in java, write this:

public class foo { ... } public class bar { public foo foo; ... }

how can write similar in ruby?

class foo end class bar attr_accessor :foo def initialize (foo) @foo = foo end end foo = foo.new bar = bar.new(foo) puts bar.foo

for say, seems need kind of type safety. can accomplish doing

def initialize (foo)   raise argumenterror, "you must provide valid foo instance" unless foo.instace_of?(foo)   @foo = foo end

ruby oop associations

JC