Module: ActiveRecord::Singleton

Defined in:
lib/acts_as_singleton.rb

Overview

A lightweight singleton library for your Active Record models.

class HomepageSettings < ActiveRecord::Base
  include ActiveRecord::Singleton
end

HomepageSettings.instance # => #<Homepage...>

Like Ruby’s built-in module, it will not prevent you from instantiating more than one object, but it will make it more difficult.

HomepageSettings.__send__(:new).new_record? # => true

Most methods assuming more than one database record will be made private upon including this module. Make sure your public class methods do not clash with the ActiveRecord::Singleton::PRIVATE pattern, or define them after including the module.

Constant Summary collapse

VERSION = 
"0.0.8"
PRIVATE =

This pattern matches methods that should be made private because they should not be used in singleton classes.

/^all$|create(?!_reflection|_callback)|find(?!er|_callback)|firs|mini|max|new|d_sco|^upd/

Class Method Summary collapse

Class Method Details

.included(model) ⇒ Object 



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# File 'lib/acts_as_singleton.rb', line 27

def self.included(model)
  model.class_eval do
    private_class_method *methods.grep(PRIVATE) # Deny existent others.

    class << self
      def exists? # Refuse arguments.
        super
      end

      # Returns the first (presumably only) record in the database, or
      # creates one.
      #
      # If validation fails on creation, it will return an unsaved object.
      #
      #   HomepageSettings.instance.update_attributes :welcome => "Hello!"
      def instance
        first || create
      end

      def inspect
        super.sub(/id: .+?, /) {} # Irrelevant.
      end

      def find(*)
        unless caller.first.include?("lib/active_record")
          raise NoMethodError,
            "private method `find' called for #{inspect}"
        end
        super
      end

      def find_by_sql(*)
        unless caller.first.include?("lib/active_record")
          raise NoMethodError,
            "private method `find_by_sql' called for #{inspect}"
        end
        super
      end
    end

    def clone
      raise TypeError, "can't clone instance of singleton #{self.class}"
    end

    def dup
      raise TypeError, "can't dup instance of singleton #{self.class}"
    end

    def inspect
      super.sub(/id: .+?, /) {} # Irrelevant.
    end
  end
end