EachWithEffect module for Ruby

each_with_effect.rb

module EachWithEffect
  DEFAULT = Object.new.freeze

  def each_with_effect(effect_handlers = {}, &block)
    effect = catch(:effect) do
      block.call(self.peek)
    end
    if effect
      handler = effect_handlers.find{ |k, v| k === effect }&.last || effect_handlers.fetch(DEFAULT)
      alternative = handler.call(effect) if handler
      block.call(alternative) if alternative
    end
    begin
      self.next
      each_with_effect(effect_handlers, &block)
    rescue StopIteration
      # Do nothing
    end
  end
end

class Enumerator
  include EachWithEffect
end

class Array
  def each_with_effect(effect_handlers = {}, &block)
    to_enum.each_with_effect(effect_handlers, &block)
  end
end

[1, '2', 3, [4, 5]].each_with_effect(
    String => ->(s) { s.to_i },
    Array => ->(a) { a.sum },
    EachWithEffect::DEFAULT => ->(o) { 42 }
) do |i|
  throw(:effect, i) unless i.is_a?(Integer)

  p i
  nil
end
# => 1, 2, 3, 9