Fix member association filtering

lib/groupify/adapter/active_record/group.rb

@@ -145,23 +145,7 @@ def associate_member_class(member_klass)
 
         def define_member_association(member_klass, association_name = nil)
           association_name ||= member_klass.model_name.plural.to_sym
-          source_type = member_klass.base_class
-
-          if ActiveSupport::VERSION::MAJOR > 3
-            has_many association_name,
-                     ->{ uniq },
-                     through: :group_memberships_as_group,
-                     source: :member,
-                     source_type: source_type,
-                     extend: MemberAssociationExtensions
-          else
-            has_many association_name,
-                     uniq: true,
-                     through: :group_memberships_as_group,
-                     source: :member,
-                     source_type: source_type,
-                     extend: MemberAssociationExtensions
-          end
+          has_many association_name, *association_options(member_klass)
 
           define_method(association_name) do |*args|
             opts = args.extract_options!
@@ -173,6 +157,33 @@ def define_member_association(member_klass, association_name = nil)
             end
           end
         end
+
+        def association_options(member_klass)
+          source_type = member_klass.base_class
+          using_sti = (member_klass.base_class != member_klass)
+
+          base_options = {
+            through: :group_memberships_as_group,
+            source: :member,
+            source_type: source_type,
+            extend: MemberAssociationExtensions
+          }
+
+          if ActiveSupport::VERSION::MAJOR > 3
+            filter = using_sti ? -> { uniq.where("#{member_klass.table_name}.type = ?", member_klass.name.to_s) } : -> { uniq }
+
+            [
+              filter,
+              base_options
+            ]
+          else
+            options = base_options.merge(uniq: true)
+            if using_sti
+              options.merge!(conditions: ["#{member_klass.table_name}.type = ?", member_klass.name.to_s])
+            end
+            [options]
+          end
+        end
       end
     end
   end

spec/active_record_spec.rb

@@ -186,6 +186,15 @@ class ProjectMember < ActiveRecord::Base
         expect(group.namespaced_members).to include(namespaced_member)
       end
 
+      it "adds a model using STI to a group" do
+        manager = Manager.create!
+        user = User.create!
+        organization = Organization.create!
+        organization.add(manager, user)
+        expect(organization.users).to match_array [user, manager]
+        expect(organization.managers).to match_array [manager]
+      end
+
       it "adds multiple members to a group" do
         group.add(user, widget)
         expect(group.users).to include(user)