Hash Driven Development

hash_object.rb

class HashObject
  def []=(method_name, implementation)
    define_singleton_method(method_name, &implementation)
  end

  def [](method_name)
    if method(method_name).arity == 0
      method(method_name).call
    else
      method(method_name).curry
    end
  end
end

NewHashObject = lambda { HashObject.new }

> hash_object = NewHashObject[]
=> #<HashObject:0x007f97c34d3098>
> hash_object[:test] = -> (foo, bar, baz) { [foo, bar, baz].join }
=> #<Proc:0x007f97c34c9e58@(irb):57 (lambda)>
> hash_object[:test]['foo']['bar']['baz']
=> "foobarbaz"