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Основы языка Ruby — Модули — композиция поведения без наследования

Фрагмент из «Основы языка Ruby»: Модули — композиция поведения без наследования.

ruby rubyencyclopedia1 embed URL статья в энциклопедии
Ruby main.rb 
module Loggable
  def log(message)
    puts "[#{Time.now}] #{message}"
  end
end

module Retryable
  def with_retry(max: 3)
    yield
  rescue => e
    retry if (max -= 1) > 0
    raise
  end
end

class Downloader
  include Loggable
  include Retryable

  def fetch(url)
    with_retry do
      log("Fetching #{url}")
      Net::HTTP.get(URI(url))  # require 'net/http'; require 'uri'
    end
  end
end
module Loggable
  def log(message)
    puts "[#{Time.now}] #{message}"
  end
end

module Retryable
  def with_retry(max: 3)
    yield
  rescue => e
    retry if (max -= 1) > 0
    raise
  end
end

class Downloader
  include Loggable
  include Retryable

  def fetch(url)
    with_retry do
      log("Fetching #{url}")
      Net::HTTP.get(URI(url))  # require 'net/http'; require 'uri'
    end
  end
end