Question

How does ruby call varz method by using varz[:foo]?

class Component
  class << self
    def varz
      @varz ||= Hash.new
    end
  end
end

Component.varz[:foo] = 'bar'
puts Component.varz # {:foo=>"bar"}

Answer 1

You cut it in the wrong way. Component.varz is a method call. To the result of it (which is a hash), [:foo] = applies. The [] and []= methods are special in that you don’t put a period between the receiver and the method.