Example of "Naught" ( https://github.com/avdi/naught )

naught_example.rb

class NullObjectExample
  require 'naught'

  NullObject = Naught.build

  def null_object
    null = NullObject.new
    null.foo                        # => nil
    null.bar                        # => nil
  end
end

class BlackHoleExample
  require 'naught'

  BlackHole = Naught.build do |config|
    config.black_hole
  end

  def black_hole
    null = BlackHole.new
    null.foo                           # => <null>
    null.foo.bar.baz                   # => <null>
    null << "hello" << "world"         # => <null>
  end
end

class MimicExample
  require 'naught'

  NullIO = Naught.build do |config|
    config.mimic IO
  end

  def mimic
    null_io = NullIO.new

    null_io << "foo"                # => nil
    null_io.readline                # => nil
    null_io.foobar                  # =>
    # undefined method `foobar' for <null:IO>:MimicExample::NullIO (NoMethodError)
  end
end

class MimicDefineMethodExample
  require 'naught'

  NullIO = Naught.build do |config|
    config.mimic IO

    def relation
      true
    end

    def readline
      "This is mimic!"
    end
  end

  def mimic
    null_io = NullIO.new

    null_io << "foo"           # => nil
    null_io.relation           # => true
    null_io.readline           # => "This is mimic!"
  end
end

module PracticalExample
  # 偽のAPI
  module Hogehoge
    module Type
      class Record
        def initialize(_args); end
      end
    end

    class Api
      def initialize(_init_params); end

      def register(_record)
        raise "Mimicになっていればここには到達しない"
      end

      def bulk_register(_records)
        raise "Mimicになっていればここには到達しない"
      end
    end
  end

  # APIを利用するクラス
  class HogehogeApiAdapter
    require 'naught'

    NullObject = Naught.build { |config| config.singleton }
    HogehogeApiMimic = Naught.build do |config|
      config.mimic Hogehoge::Api
    end

    def initialize(init_params)
      # 実際には、決め打ちでfalseにしている部分を環境の判別にする
      @api = false ? Hogehoge::Api(init_params).new : HogehogeApiMimic.new
    end

    # Hogehoge::Apiに生えているメソッドは全て握り潰されるので、APIクラスの先にある実装を意識する必要がない
    def insert(args)
      record = Hogehoge::Type::Record.new(args)
      @api.register(record)
    end

    def bulk_insert(args_array)
      records = args_array.map { |args| Hogehoge::Type::Record.new(args) }
      @api.bulk_register(records)
    end
  end
end