Added ActiveRecord::Base.store for declaring simple single-column key/value stores [DHH]

activerecord/CHANGELOG

@@ -1,5 +1,16 @@
 *Rails 3.2.0 (unreleased)*
 
+* Added ActiveRecord::Base.store for declaring simple single-column key/value stores [DHH]
+
+    class User < ActiveRecord::Base
+      store :settings, accessors: [ :color, :homepage ]
+    end
+    
+    u = User.new(color: 'black', homepage: '37signals.com')
+    u.color                          # Accessor stored attribute
+    u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
+
+
 * MySQL: case-insensitive uniqueness validation avoids calling LOWER when
   the column already uses a case-insensitive collation. Fixes #561.
 

activerecord/lib/active_record.rb

@@ -69,6 +69,7 @@ module ActiveRecord
     autoload :Schema
     autoload :SchemaDumper
     autoload :Serialization
+    autoload :Store
     autoload :SessionStore
     autoload :Timestamp
     autoload :Transactions

activerecord/lib/active_record/base.rb

@@ -2145,7 +2145,7 @@ MSG
     # AutosaveAssociation needs to be included before Transactions, because we want
     # #save_with_autosave_associations to be wrapped inside a transaction.
     include AutosaveAssociation, NestedAttributes
-    include Aggregations, Transactions, Reflection, Serialization
+    include Aggregations, Transactions, Reflection, Serialization, Store
 
     NilClass.add_whiner(self) if NilClass.respond_to?(:add_whiner)
 

activerecord/lib/active_record/store.rb

@@ -0,0 +1,49 @@
+module ActiveRecord
+  # Store gives you a thin wrapper around serialize for the purpose of storing hashes in a single column.
+  # It's like a simple key/value store backed into your record when you don't care about being able to
+  # query that store outside the context of a single record.
+  #
+  # You can then declare accessors to this store that are then accessible just like any other attribute
+  # of the model. This is very helpful for easily exposing store keys to a form or elsewhere that's
+  # already built around just accessing attributes on the model.
+  #
+  # Make sure that you declare the database column used for the serialized store as a text, so there's
+  # plenty of room.
+  #
+  # Examples:
+  #
+  #   class User < ActiveRecord::Base
+  #     store :settings, accessors: [ :color, :homepage ]
+  #   end
+  #   
+  #   u = User.new(color: 'black', homepage: '37signals.com')
+  #   u.color                          # Accessor stored attribute
+  #   u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
+  #
+  #   # Add additional accessors to an existing store through store_accessor
+  #   class SuperUser < User
+  #     store_accessor :settings, :privileges, :servants
+  #   end
+  module Store
+    extend ActiveSupport::Concern
+  
+    module ClassMethods
+      def store(store_attribute, options = {})
+        serialize store_attribute, Hash
+        store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
+      end
+
+      def store_accessor(store_attribute, *keys)
+        Array(keys).flatten.each do |key|
+          define_method("#{key}=") do |value|
+            send(store_attribute)[key] = value
+          end
+    
+          define_method(key) do
+            send(store_attribute)[key]
+          end
+        end
+      end
+    end
+  end
+end

activerecord/test/cases/store_test.rb

@@ -0,0 +1,29 @@
+require 'cases/helper'
+require 'models/admin'
+require 'models/admin/user'
+
+class StoreTest < ActiveRecord::TestCase
+  setup do
+    @john = Admin::User.create(name: 'John Doe', color: 'black')
+  end
+  
+  test "reading store attributes through accessors" do
+    assert_equal 'black', @john.color
+    assert_nil @john.homepage
+  end
+
+  test "writing store attributes through accessors" do
+    @john.color = 'red'
+    @john.homepage = '37signals.com'
+
+    assert_equal 'red', @john.color
+    assert_equal '37signals.com', @john.homepage
+  end
+  
+  test "accessing attributes not exposed by accessors" do
+    @john.settings[:icecream] = 'graeters'
+    @john.save
+
+    assert 'graeters', @john.reload.settings[:icecream]
+  end
+end

activerecord/test/models/admin/user.rb

@@ -1,3 +1,4 @@
 class Admin::User < ActiveRecord::Base
   belongs_to :account
+  store :settings, accessors: [ :color, :homepage ]
 end

activerecord/test/schema/schema.rb

@@ -37,6 +37,7 @@ ActiveRecord::Schema.define do
 
   create_table :admin_users, :force => true do |t|
     t.string :name
+    t.text :settings
     t.references :account
   end