Added extension capabilities to has_many and has_and_belongs_to_many proxies [DHH]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2861 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Added extension capabilities to has_many and has_and_belongs_to_many proxies [DHH]. Example:
+
+    class Account < ActiveRecord::Base
+      has_many :people, :extend => Module.new {
+        def find_or_create_by_name(name)
+          first_name, *last_name = name.split
+          last_name = last_name.join " "
+    
+          find_by_first_name_and_last_name(first_name, last_name) ||
+            create({ :first_name => first_name, :last_name => last_name })
+        end
+      }
+    end
+ 
+    person = Account.find(:first).people.find_or_create_by_name("David Heinemeier Hansson")
+    person.first_name # => "David"
+    person.last_name  # => "Heinemeier Hansson"
+ 
+  Note that the anoymous module must be declared using brackets, not do/end (due to order of evaluation).
+ 
+
 * A missing primary key column shouldn't raise an error when generating its error message.  [Don Park <don.park@gmail.com>]
 
 * Changed :dbfile to :database for SQLite adapter for consistency (old key still works as an alias) #2644 [Dan Peterson]

activerecord/lib/active_record/associations.rb

@@ -120,6 +120,30 @@ def clear_association_cache #:nodoc:
     # Should any of the before_add callbacks throw an exception, the object does not get added to the collection. Same with
     # the before_remove callbacks, if an exception is thrown the object doesn't get removed.
     #
+    # === Association extensions
+    #
+    # The proxy objects that controls the access to associations can be extended through anonymous modules. This is especially
+    # beneficial for adding new finders, creators, and other factory-type methods that are only used as part of this associatio.
+    # Example:
+    #
+    #   class Account < ActiveRecord::Base
+    #     has_many :people, :extend => Module.new {
+    #       def find_or_create_by_name(name)
+    #         first_name, *last_name = name.split
+    #         last_name = last_name.join " "
+    #   
+    #         find_by_first_name_and_last_name(first_name, last_name) ||
+    #           create({ :first_name => first_name, :last_name => last_name })
+    #       end
+    #     }
+    #   end
+    #
+    #   person = Account.find(:first).people.find_or_create_by_name("David Heinemeier Hansson")
+    #   person.first_name # => "David"
+    #   person.last_name  # => "Heinemeier Hansson"
+    #
+    # Note that the anoymous module must be declared using brackets, not do/end (due to order of evaluation).
+    #
     # == Caching
     #
     # All of the methods are built on a simple caching principle that will keep the result of the last query around unless specifically
@@ -282,6 +306,7 @@ module ClassMethods
       #   associations that depend on multiple tables. Note: When this option is used, +find_in_collection+ is _not_ added.
       # * <tt>:counter_sql</tt>  - specify a complete SQL statement to fetch the size of the association. If +:finder_sql+ is
       #   specified but +:counter_sql+, +:counter_sql+ will be generated by replacing SELECT ... FROM with SELECT COUNT(*) FROM.
+      # * <tt>:extend</tt>  - anonymous module for extending the proxy, see "Association extensions".
       #
       # Option examples:
       #   has_many :comments, :order => "posted_on"
@@ -296,7 +321,7 @@ def has_many(association_id, options = {})
         options.assert_valid_keys(
           :foreign_key, :class_name, :exclusively_dependent, :dependent, 
           :conditions, :order, :finder_sql, :counter_sql, 
-          :before_add, :after_add, :before_remove, :after_remove 
+          :before_add, :after_add, :before_remove, :after_remove, :extend
         )
 
         association_name, association_class_name, association_class_primary_key_name =
@@ -380,7 +405,7 @@ def has_many(association_id, options = {})
       #   has_one :last_comment, :class_name => "Comment", :order => "posted_on"
       #   has_one :project_manager, :class_name => "Person", :conditions => "role = 'project_manager'"
       def has_one(association_id, options = {})
-        options.assert_valid_keys(:class_name, :foreign_key, :remote, :conditions, :order, :dependent, :counter_cache)
+        options.assert_valid_keys(:class_name, :foreign_key, :remote, :conditions, :order, :dependent, :counter_cache, :extend)
 
         association_name, association_class_name, association_class_primary_key_name =
             associate_identification(association_id, options[:class_name], options[:foreign_key], false)
@@ -460,7 +485,7 @@ def has_one(association_id, options = {})
       #   belongs_to :valid_coupon, :class_name => "Coupon", :foreign_key => "coupon_id", 
       #              :conditions => 'discounts > #{payments_count}'
       def belongs_to(association_id, options = {})
-        options.assert_valid_keys(:class_name, :foreign_key, :remote, :conditions, :order, :dependent, :counter_cache)
+        options.assert_valid_keys(:class_name, :foreign_key, :remote, :conditions, :order, :dependent, :counter_cache, :extend)
 
         association_name, association_class_name, class_primary_key_name =
             associate_identification(association_id, options[:class_name], options[:foreign_key], false)
@@ -569,6 +594,7 @@ def belongs_to(association_id, options = {})
       #   classes with a manual one
       # * <tt>:insert_sql</tt> - overwrite the default generated SQL used to add links between the associated classes
       #   with a manual one
+      # * <tt>:extend</tt>  - anonymous module for extending the proxy, see "Association extensions".
       #
       # Option examples:
       #   has_and_belongs_to_many :projects
@@ -580,7 +606,7 @@ def has_and_belongs_to_many(association_id, options = {})
         options.assert_valid_keys(
           :class_name, :table_name, :foreign_key, :association_foreign_key, :conditions,
           :join_table, :finder_sql, :delete_sql, :insert_sql, :order, :uniq, :before_add, :after_add, 
-          :before_remove, :after_remove
+          :before_remove, :after_remove, :extend
         )
 
         association_name, association_class_name, association_class_primary_key_name =

activerecord/lib/active_record/associations/association_proxy.rb

@@ -2,7 +2,8 @@ module ActiveRecord
   module Associations
     class AssociationProxy #:nodoc:
       alias_method :proxy_respond_to?, :respond_to?
-      instance_methods.each { |m| undef_method m unless m =~ /(^__|^nil\?|^proxy_respond_to\?|^send)/ }
+      alias_method :proxy_extend, :extend
+      instance_methods.each { |m| undef_method m unless m =~ /(^__|^nil\?|^proxy_respond_to\?|^proxy_extend|^send)/ }
 
       def initialize(owner, association_name, association_class_name, association_class_primary_key_name, options)
         @owner = owner
@@ -11,6 +12,8 @@ def initialize(owner, association_name, association_class_name, association_clas
         @association_class = eval(association_class_name, nil, __FILE__, __LINE__)
         @association_class_primary_key_name = association_class_primary_key_name
 
+        proxy_extend(options[:extend]) if options[:extend]
+
         reset
       end
       
@@ -95,4 +98,4 @@ def raise_on_type_mismatch(record)
         end
     end
   end
-end
+end
\ No newline at end of file

activerecord/test/associations_extensions_test.rb

+require 'abstract_unit'
+require 'fixtures/project'
+require 'fixtures/developer'
+
+class AssociationsExtensionsTest < Test::Unit::TestCase
+  fixtures :projects, :developers
+
+  def test_extension_on_habtm
+    assert_equal projects(:action_controller), developers(:david).projects.find_most_recent
+  end
+  
+  def test_extension_on_has_many
+    assert_equal comments(:more_greetings), posts(:welcome).comments.find_most_recent
+  end
+end
\ No newline at end of file

activerecord/test/fixtures/developer.rb

 class Developer < ActiveRecord::Base
-  has_and_belongs_to_many :projects
+  has_and_belongs_to_many :projects, :extend => Module.new {
+    def find_most_recent
+      find(:first, :order => "id DESC")
+    end
+  }
+
+
   has_and_belongs_to_many :special_projects, :join_table => 'developers_projects', :association_foreign_key => 'project_id'
 
   validates_inclusion_of :salary, :in => 50000..200000

activerecord/test/fixtures/post.rb

 class Post < ActiveRecord::Base
-  belongs_to :author
-  has_many   :comments, :order => "body"
-  has_one    :very_special_comment, :class_name => "VerySpecialComment"
+  belongs_to :author, :extend => Module.new {
+    def greeting
+      "hello"
+    end
+  }
+
+  has_many   :comments, :order => "body", :extend => Module.new {
+    def find_most_recent
+      find(:first, :order => "id DESC")
+    end
+  }
+
+
   has_many   :special_comments, :class_name => "SpecialComment"
   has_and_belongs_to_many :categories
   has_and_belongs_to_many :special_categories, :join_table => "categories_posts"