Introduce dynamic scopes for ActiveRecord: you can now use class methods like...

Introduce dynamic scopes for ActiveRecord: you can now use class methods like scoped_by_user_name(user_name) and scoped_by_user_name_and_password(user_name, password) that will use the scoped method with attributes you supply. [#1648 state:committed]
Signed-off-by: NDavid Heinemeier Hansson <david@loudthinking.com>

activerecord/CHANGELOG

 *2.3.0/3.0*
 
+* Added dynamic scopes ala dynamic finders #1648 [Yaroslav Markin]
+
 * Fixed that ActiveRecord::Base#new_record? should return false (not nil) for existing records #1219 [Yaroslav Markin]
 
 * I18n the word separator for error messages. Introduces the activerecord.errors.format.separator translation key.  #1294 [Akira Matsuda]

activerecord/lib/active_record.rb

@@ -51,6 +51,7 @@ def self.load_all!
   autoload :Callbacks, 'active_record/callbacks'
   autoload :Dirty, 'active_record/dirty'
   autoload :DynamicFinderMatch, 'active_record/dynamic_finder_match'
+  autoload :DynamicScopeMatch, 'active_record/dynamic_scope_match'
   autoload :Migration, 'active_record/migration'
   autoload :Migrator, 'active_record/migration'
   autoload :NamedScope, 'active_record/named_scope'

activerecord/lib/active_record/base.rb

@@ -1456,7 +1456,10 @@ def abstract_class?
       def respond_to?(method_id, include_private = false)
         if match = DynamicFinderMatch.match(method_id)
           return true if all_attributes_exists?(match.attribute_names)
+        elsif match = DynamicScopeMatch.match(method_id)
+          return true if all_attributes_exists?(match.attribute_names)
         end
+        
         super
       end
 
@@ -1809,7 +1812,11 @@ def undecorated_table_name(class_name = base_class.name)
         # This also enables you to initialize a record if it is not found, such as find_or_initialize_by_amount(amount)
         # or find_or_create_by_user_and_password(user, password).
         #
-        # Each dynamic finder or initializer/creator is also defined in the class after it is first invoked, so that future
+        # Also enables dynamic scopes like scoped_by_user_name(user_name) and scoped_by_user_name_and_password(user_name, password) that
+        # are turned into scoped(:conditions => ["user_name = ?", user_name]) and scoped(:conditions => ["user_name = ? AND password = ?", user_name, password])
+        # respectively.
+        #
+        # Each dynamic finder, scope or initializer/creator is also defined in the class after it is first invoked, so that future
         # attempts to use it do not run through method_missing.
         def method_missing(method_id, *arguments, &block)
           if match = DynamicFinderMatch.match(method_id)
@@ -1868,6 +1875,22 @@ def self.#{method_id}(*args)
               }, __FILE__, __LINE__
               send(method_id, *arguments, &block)
             end
+          elsif match = DynamicScopeMatch.match(method_id)
+            attribute_names = match.attribute_names
+            super unless all_attributes_exists?(attribute_names)
+            if match.scope?
+              self.class_eval %{
+                def self.#{method_id}(*args)                        # def self.scoped_by_user_name_and_password(*args)
+                  options = args.extract_options!                   #   options = args.extract_options!
+                  attributes = construct_attributes_from_arguments( #   attributes = construct_attributes_from_arguments(
+                    [:#{attribute_names.join(',:')}], args          #     [:user_name, :password], args
+                  )                                                 #   )
+                                                                    # 
+                  scoped(:conditions => attributes)                 #   scoped(:conditions => attributes)
+                end                                                 # end
+              }, __FILE__, __LINE__
+              send(method_id, *arguments)
+            end
           else
             super
           end

activerecord/lib/active_record/dynamic_scope_match.rb

+module ActiveRecord
+  class DynamicScopeMatch
+    def self.match(method)
+      ds_match = self.new(method)
+      ds_match.scope ? ds_match : nil
+    end
+
+    def initialize(method)
+      @scope = true
+      case method.to_s
+      when /^scoped_by_([_a-zA-Z]\w*)$/
+        names = $1
+      else
+        @scope = nil
+      end
+      @attribute_names = names && names.split('_and_')
+    end
+
+    attr_reader :scope, :attribute_names
+
+    def scope?
+      !@scope.nil?
+    end
+  end
+end

activerecord/test/cases/named_scope_test.rb

@@ -278,3 +278,23 @@ def test_chaining_with_duplicate_joins
     assert_equal post.comments.size, Post.scoped(:joins => join).scoped(:joins => join, :conditions => "posts.id = #{post.id}").size
   end
 end
+
+class DynamicScopeMatchTest < ActiveRecord::TestCase  
+  def test_scoped_by_no_match
+    assert_nil ActiveRecord::DynamicScopeMatch.match("not_scoped_at_all")
+  end
+
+  def test_scoped_by
+    match = ActiveRecord::DynamicScopeMatch.match("scoped_by_age_and_sex_and_location")
+    assert_not_nil match
+    assert match.scope?
+    assert_equal %w(age sex location), match.attribute_names
+  end
+end
+
+class DynamicScopeTest < ActiveRecord::TestCase
+  def test_dynamic_scope
+    assert_equal Post.scoped_by_author_id(1).find(1), Post.find(1)
+    assert_equal Post.scoped_by_author_id_and_title(1, "Welcome to the weblog").first, Post.find(:first, :conditions => { :author_id => 1, :title => "Welcome to the weblog"})
+  end
+end