Approach to save all metadata in single column

README.rdoc

@@ -14,10 +14,7 @@ Add the following line to your Gemfile:
     include CarrierWave::RMagick
     include CarrierWave::Meta
 
-    storage :file
-
     process :store_meta => [{md5sum: true}]
-
     version :version do
       process :resize_to_fill => [200, 200]
       process :store_meta
@@ -44,21 +41,24 @@ Add the following line to your Gemfile:
 
 = Saving values to database
 
-Simply create database columns to hold metadata in your model's table. Currently gem supports width, height,
-image_size ([width, height]), content_type, file_size and MD5 fields. Versions are supported too.
+Simply create database columns to hold metadata in your model's table. Currently
+gem supports width, height, image_size ([width, height]), content_type,
+file_size and MD5 fields. Versions are supported too.
 
   class TestModel
     attr_accessor :image_width
     attr_accessor :image_height
     attr_accessor :image_image_size
     attr_accessor :image_content_type
     attr_accessor :image_file_size
+    attr_accessor :image_md5sum
 
     attr_accessor :image_version_width
     attr_accessor :image_version_height
     attr_accessor :image_version_image_size
     attr_accessor :image_version_content_type
     attr_accessor :image_version_file_size
+    attr_accessor :image_version_md5sum
   end
 
   file = File.open('test.jpg')
@@ -73,19 +73,49 @@ image_size ([width, height]), content_type, file_size and MD5 fields. Versions a
 
 When columns are available in the model instance, metadata is stored in that columns.
 
+= Saving values in the single column
+
+For now, works only for ActiveRecord.
+
+  ```ruby
+  class TestModel < ActiveRecord::Base
+    extend CarrierWave::Meta::ActiveRecord
+
+    mount_uploader :image, TestUploader
+    serialize :image_meta, OpenStruct
+    carrierwave_meta_composed :image_meta,
+      :image, image_version: [:width, :height, :md5sum]
+  end
+
+  model = TestModel.new
+  model.image.store!('test.jpg')
+  model.image_width         # 200
+  model.image_version_width # 200
+  model.image_meta          # {image_width: 200, image_height: 200, ...}
+  ```
+
+All you need is image_meta column, all other attributes are virtual. Note
+that carrierwave_meta_composed should be called after mounting uploader.
+
 = Behind the scenes
 
-After the file is retrieved from store or cache metadata is recalculated unless uploader has attached
-model instance. If uploader has attached model instance values are read from that instance.
+After the file is retrieved from store or cache metadata is recalculated
+unless uploader has attached model instance. If uploader has attached
+model instance values are read from that instance.
 
   uploader = TestUploader.new
   uploader.retrieve_from_store!('test.jpg')
-
   uploader.version.width # 200
 
+  model = TestModel.new
+  model.image.store!('test.jpg')
+  model.image_width # 200
+  model.image.width # 200, actually read from image_width
+
 = model_delegate_attribute
 
-Used to synchronize data between uploader and mounted model instance. Model's instance is used like value cache.
+Is used to synchronize data between uploader and mounted model instance.
+Model's instance is used like value cache.
 
   class DelegateTestModel
     attr_accessor :processed
@@ -128,8 +158,10 @@ Used to synchronize data between uploader and mounted model instance. Model's in
 
 When model is mounted to uploader:
 
-1. If attribute is assigned inside uploader then corresponding property in model is also assigned.
-2. If attribute is retrieved from uploader instance first checks that value is defined in model and returns it. Otherwise returns uploader's instance variable.
+1. If attribute is assigned inside uploader then corresponding property
+in model is also assigned.
+2. If attribute is retrieved from uploader, uploader checks that value is
+defined in model and returns it. Otherwise returns uploader's instance variable.
 3. If file is deleted, value becomes nil.
 
 Otherwise acts as regular uploader's instance variables.

carrierwave-meta.gemspec

@@ -30,4 +30,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency(%q<carrierwave-vips>)
   s.add_development_dependency(%q<fog>, '~> 1.3.1')
   s.add_development_dependency(%q<simplecov>)
+  s.add_development_dependency(%q<activerecord>, '>= 3.0')
 end

lib/carrierwave-meta.rb

@@ -4,3 +4,4 @@
 require 'carrierwave-meta/version'
 require 'carrierwave-meta/model_delegate_attribute'
 require 'carrierwave-meta/meta'
+require 'carrierwave-meta/active_record'

lib/carrierwave-meta/active_record.rb

@@ -0,0 +1,22 @@
+module CarrierWave
+  module Meta
+    module ActiveRecord
+      ALLOWED = %w(width height md5sum image_size file_size content_type)
+
+      def carrierwave_meta_composed(single_attribute, *args)
+        defined_attrs = args.map do |arg|
+          name, to_define = if arg.is_a?(Symbol)
+            [arg, ALLOWED]
+          elsif arg.is_a?(Hash)
+            [arg.keys.first, arg.values.first]
+          end
+
+          to_define.map do |attr|
+            delegate :"#{name}_#{attr}", to: single_attribute, allow_nil: true
+            delegate :"#{name}_#{attr}=", to: single_attribute, allow_nil: true
+          end
+        end
+      end
+    end
+  end
+end

spec/modules/active_record_spec.rb

@@ -0,0 +1,31 @@
+require 'spec_helper'
+
+describe CarrierWave::Meta::ActiveRecord do
+  let(:model) { TestComposedModel.new }
+  let(:model_with_image) do
+    model.tap do |m|
+      m.image = File.open('spec/fixtures/big.jpg')
+      m.save!
+    end
+  end
+
+  it "model's virtual meta attributes must exists" do
+    subject::ALLOWED.each do |name|
+      model.should respond_to(:"image_#{name}")
+    end
+  end
+
+  it "must assign model's virtual attributes and save meta column" do
+    subject::ALLOWED.each do |name|
+      model_with_image.send(:"image_#{name}").should_not be_blank
+    end
+
+    model_with_image.image_version_width.should_not be_blank
+    model_with_image.image_version_height.should_not be_blank
+
+    model_with_image.reload
+
+    model_with_image.image_version_width.should_not be_blank
+    model_with_image.image_version_height.should_not be_blank
+  end
+end

spec/spec_helper.rb

@@ -5,8 +5,11 @@
 require 'simplecov'
 require 'mime/types'
 require 'carrierwave'
+require 'carrierwave/orm/activerecord'
 require 'support/remote'
 require 'support/current_processor'
+require 'active_record'
+require 'support/schema'
 
 SimpleCov.start
 
@@ -24,16 +27,9 @@
 require 'support/test_blank_uploader'
 require 'support/test_uploader'
 require 'support/test_model'
+require 'support/test_composed_model'
 require 'fog'
 
-=begin
-class CarrierWave::Storage::Fog::File
-  def original_filename
-    ::File.basename(path)
-  end
-end
-=end
-
 RSpec.configure do |config|
   config.before do
     FileUtils.rm_rf('tmp')

spec/support/schema.rb

@@ -1,15 +1,10 @@
-ActiveRecord::Schema.define :version => 0 do
-  create_table "test_models", :force => true do |t|
-    t.string :image
-
-    t.integer :image_width
-    t.integer :image_height
-    t.string  :image_content_type
-    t.integer :image_file_size
+ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :database => ":memory:")
+
+ActiveRecord::Schema.define :version => 1 do
 
-    t.integer :image_version_width
-    t.integer :image_version_height
-    t.integer :image_version_file_size
-    t.string  :image_version_content_type
+  create_table "test_composed_models", :force => true do |t|
+    t.string :image
+    t.text :image_meta
   end
+
 end

spec/support/test_composed_model.rb

@@ -0,0 +1,7 @@
+class TestComposedModel < ActiveRecord::Base
+  extend CarrierWave::Meta::ActiveRecord
+
+  mount_uploader :image, TestUploader
+  serialize :image_meta, OpenStruct
+  carrierwave_meta_composed :image_meta, :image, image_version: [:width, :height]
+end