Trashable 'concern' for Rails models

20120625030355_add_deleted_at_to_user.rb

# db/migrate/20120625030355_add_deleted_at_to_user.rb

class AddDeletedAtToUser < ActiveRecord::Migration
  def change
    add_column :users, :deleted_at, :time
  end
end

application.rb

# config/application.rb

module YourApp
  class Application < Rails::Application
    config.autoload_paths += %W(
      #{config.root}/lib
      #{config.root}/app/controllers/concerns
      #{config.root}/app/models/concerns
    )
end

trashable.rb

# app/models/concerns/trashable.rb

module Trashable
  extend ActiveSupport::Concern

  included do
    default_scope where(deleted_at: nil)
  end

  module ClassMethods
    def trashed
      self.unscoped.where(self.arel_table[:deleted_at].not_eq(nil))
    end
  end

  def trash
    run_callbacks :destroy do
      update_column :deleted_at, Time.now
    end
  end

  def recover
    # update_column not appropriate here as it uses the default scope
    update_attribute :deleted_at, nil
  end
end

user.rb

# app/models/user.rb

class User < ActiveRecord::Base
  include Trashable
end

I like to override #destroy like this so that dependent models are protected during 'dependent: :destroy' callbacks.

def destroy
  self.trash
end

For example, this way, the comments of a user will be trashed rather than destroyed in a situation like the one below.

class User < ApplicationRecord
  include Trashable
  has_many :comments, dependent: :destroy
end

class Comment < ApplicationRecord
  include Trashable
  belongs_to :user
end

Now it'd be nice if #recover could handle recovering trashed dependents.