Use proper objects to do the work to build the associations (adding methods, callbacks etc) rather than calling a whole bunch of methods with rather long names.

1 files changed, 63 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
new file mode 100644
index 0000000000..e40b32826a
--- /dev/null
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -0,0 +1,63 @@
+module ActiveRecord::Associations::Builder
+  class HasAndBelongsToMany < CollectionAssociation #:nodoc:
+    self.macro = :has_and_belongs_to_many
+
+    self.valid_options += [:join_table, :association_foreign_key, :delete_sql, :insert_sql]
+
+    def build
+      reflection = super
+      check_validity(reflection)
+      redefine_destroy
+      reflection
+    end
+
+    private
+
+      def redefine_destroy
+        # Don't use a before_destroy callback since users' before_destroy
+        # callbacks will be executed after the association is wiped out.
+        name = self.name
+        model.send(:include, Module.new {
+          class_eval <<-RUBY, __FILE__, __LINE__ + 1
+            def destroy          # def destroy
+              super              #   super
+              #{name}.clear      #   posts.clear
+            end                  # end
+          RUBY
+        })
+      end
+
+      # TODO: These checks should probably be moved into the Reflection, and we should not be
+      #       redefining the options[:join_table] value - instead we should define a
+      #       reflection.join_table method.
+      def check_validity(reflection)
+        if reflection.association_foreign_key == reflection.foreign_key
+          raise ActiveRecord::HasAndBelongsToManyAssociationForeignKeyNeeded.new(reflection)
+        end
+
+        reflection.options[:join_table] ||= join_table_name(
+          model.send(:undecorated_table_name, model.to_s),
+          model.send(:undecorated_table_name, reflection.class_name)
+        )
+
+        if model.connection.supports_primary_key? && (model.connection.primary_key(reflection.options[:join_table]) rescue false)
+          raise ActiveRecord::HasAndBelongsToManyAssociationWithPrimaryKeyError.new(reflection)
+        end
+      end
+
+      # Generates a join table name from two provided table names.
+      # The names in the join table names end up in lexicographic order.
+      #
+      #   join_table_name("members", "clubs")         # => "clubs_members"
+      #   join_table_name("members", "special_clubs") # => "members_special_clubs"
+      def join_table_name(first_table_name, second_table_name)
+        if first_table_name < second_table_name
+          join_table = "#{first_table_name}_#{second_table_name}"
+        else
+          join_table = "#{second_table_name}_#{first_table_name}"
+        end
+
+        model.table_name_prefix + join_table + model.table_name_suffix
+      end
+  end
+end