DI (IoC) container in Ruby.

container.rb

class Container
  def initialize
    @c   = {}
    @fac = {}
    yield self
  end

  def [] k
    @c[k] || (@fac[k] && @fac[k].call(self))
  end

  def []= k, v
    @c[k] = v
  end

  def factory k, &b
    @fac[k] = b
  end
end


class B
  def initialize a; @a = a; end
end
c = Container.new do |c|
  c[:a] = 42
  c[:b] = B.new c[:a]
  c.factory(:b_new){|c| B.new c[:a] }
end
p c[:a]
p c[:b]
p c[:b]
p c[:b_new]
p c[:b_new]