https://github.com/alfa-jpn/kakurenbo-puti のさらに簡易版

soft_deletable.rb

# USAGE:
#   rails g migration add_deleted_at_to_hoge_model deleted_at:datetime
#
#   class HogeModel
#     extend Extensions::SoftDeletable
#     soft_deletable
#   end
#
#
#   hoge.destroy_softly # or hoge.destroy_softly!
#   hoge.restore_soft_delete # or hoge.restore_soft_delete
#   
#   hoge.deleted?
#   hoge.living?
#
#   HogeModel.living
#   HogeModel.deleted
#
module Extensions
  module SoftDeletable

    def soft_deletable(column: :deleted_at,
        soft_delete_method_name: :destroy_softly, restore_method_name: :restore_soft_delete,
        soft_deleted_scope: :deleted, without_soft_deleted_scope: :living)


      Initializers.create_column_name_accessor(self, column)
      Initializers.create_method_name_accessor(self, soft_delete_method_name, restore_method_name)

      Initializers.create_callbacks(self)
      Initializers.create_instance_methods(self, soft_deleted_scope, without_soft_deleted_scope)
      Initializers.create_scopes(self, soft_deleted_scope, without_soft_deleted_scope)
    end

    module Initializers
      def self.create_column_name_accessor(klass, column)
        klass.class_eval do
          define_singleton_method(:soft_delete_column) { column }
          delegate :soft_delete_column, to: :class
        end
      end

      def self.create_method_name_accessor(klass, soft_delete_method_name, restore_method_name)
        klass.class_eval do
          define_singleton_method(:soft_delete_method_name) { soft_delete_method_name }
          define_singleton_method(:restore_method_name) { restore_method_name }
          delegate :soft_delete_method_name, :restore_method_name, to: :class
        end
      end

      def self.create_callbacks(klass)
        klass.class_eval do
          define_model_callbacks soft_delete_method_name
          define_model_callbacks restore_method_name
        end
      end

      def self.create_instance_methods(klass, soft_deleted_scope, without_soft_deleted_scope)
        klass.class_eval do
          define_method "#{soft_delete_method_name}!" do
            run_callbacks(soft_delete_method_name) { touch soft_delete_column; self }
          end
          define_method soft_delete_method_name do
            !! send("#{soft_delete_method_name}!") rescue nil
          end

          define_method "#{restore_method_name}!" do
            run_callbacks(restore_method_name) { update_column soft_delete_column, nil; self  }
          end
          define_method restore_method_name do
            !! send("#{restore_method_name}!") rescue nil
          end

          define_method "#{soft_deleted_scope}?" do
            send("#{soft_delete_column}?")
          end

          define_method "#{without_soft_deleted_scope}?" do
            !send("#{soft_delete_column}?")
          end
        end
      end

      def self.create_scopes(klass, soft_deleted_scope, without_soft_deleted_scope)
        klass.class_eval do
          scope soft_deleted_scope, ->{ where.not(soft_delete_column => nil) }
          scope without_soft_deleted_scope, ->{ where(soft_delete_column => nil) }
        end
      end
    end
  end
end