join_scope

# File activerecord/lib/active_record/reflection.rb, line 174
      def join_scope(table, foreign_table, foreign_klass)
        predicate_builder = predicate_builder(table)
        scope_chain_items = join_scopes(table, predicate_builder)
        klass_scope       = klass_join_scope(table, predicate_builder)

        if type
          klass_scope.where!(type => foreign_klass.polymorphic_name)
        end

        scope_chain_items.inject(klass_scope, &:merge!)

        primary_key = join_primary_key
        foreign_key = join_foreign_key

        klass_scope.where!(table[primary_key].eq(foreign_table[foreign_key]))

        if klass.finder_needs_type_condition?
          klass_scope.where!(klass.send(:type_condition, table))
        end

        klass_scope
      end