simple refactoring

app/models/users_project.rb

@@ -14,62 +14,64 @@ class UsersProject < ActiveRecord::Base
   after_save :update_repository
   after_destroy :update_repository
 
-  validates_uniqueness_of :user_id, scope: [:project_id], message: "already exists in project"
-  validates_presence_of :user_id
-  validates_presence_of :project_id
+  validates :user, presence: true
+  validates :user_id, uniqueness: { :scope => [:project_id], message: "already exists in project" }
+  validates :project, presence: true
 
   delegate :name, :email, to: :user, prefix: true
 
-  def self.bulk_delete(project, user_ids)
-    UsersProject.transaction do
-      UsersProject.where(:user_id => user_ids, :project_id => project.id).each do |users_project|
-        users_project.destroy
+  class << self
+    def bulk_delete(project, user_ids)
+      UsersProject.transaction do
+        UsersProject.where(:user_id => user_ids, :project_id => project.id).each do |users_project|
+          users_project.destroy
+        end
       end
     end
-  end
 
-  def self.bulk_update(project, user_ids, project_access)
-    UsersProject.transaction do
-      UsersProject.where(:user_id => user_ids, :project_id => project.id).each do |users_project|
-        users_project.project_access = project_access
-        users_project.save
+    def bulk_update(project, user_ids, project_access)
+      UsersProject.transaction do
+        UsersProject.where(:user_id => user_ids, :project_id => project.id).each do |users_project|
+          users_project.project_access = project_access
+          users_project.save
+        end
       end
     end
-  end
 
-  def self.bulk_import(project, user_ids, project_access)
-    UsersProject.transaction do
-      user_ids.each do |user_id|
-        users_project = UsersProject.new(
-          project_access: project_access,
-          user_id: user_id
-        )
-        users_project.project = project
-        users_project.save
+    def bulk_import(project, user_ids, project_access)
+      UsersProject.transaction do
+        user_ids.each do |user_id|
+          users_project = UsersProject.new(
+            project_access: project_access,
+            user_id: user_id
+          )
+          users_project.project = project
+          users_project.save
+        end
       end
     end
-  end
 
-  def self.user_bulk_import(user, project_ids, project_access)
-    UsersProject.transaction do
-      project_ids.each do |project_id|
-        users_project = UsersProject.new(
-          project_access: project_access,
-        )
-        users_project.project_id = project_id
-        users_project.user_id = user.id
-        users_project.save
+    def user_bulk_import(user, project_ids, project_access)
+      UsersProject.transaction do
+        project_ids.each do |project_id|
+          users_project = UsersProject.new(
+            project_access: project_access,
+          )
+          users_project.project_id = project_id
+          users_project.user_id = user.id
+          users_project.save
+        end
       end
     end
-  end
 
-  def self.access_roles
-    {
-      "Guest"     => GUEST,
-      "Reporter"  => REPORTER,
-      "Developer" => DEVELOPER,
-      "Master"    => MASTER
-    }
+    def access_roles
+      {
+        "Guest"     => GUEST,
+        "Reporter"  => REPORTER,
+        "Developer" => DEVELOPER,
+        "Master"    => MASTER
+      }
+    end
   end
 
   def role_access