Lazy: fetch deep values only when you need to

lazy.rb

# Example: Lazy.new(lambda { |id| API::HackerNews.item(id) }, 0)

class Lazy
  attr_reader :value

  def initialize(function:, value:)
    @function = function
    @value = value
    @cached = nil
    @is_cached = false
  end

  def method_missing(method, *args, &block)
    cached.send(method, *args, &block)
  end

  def cached
    unless @cached
      @cached = @function.call(value)
      @is_cached = true
    end

    @cached
  end

  def cached?
    @is_cached
  end

  def to_s
    value.to_s
  end

  def inspect
    "#<Lazy @value=#{value.inspect} cached?=#{cached?.inspect}>"
  end
end