class StudentsForCourse < ActiveRecord::Base attr_accessible :course_id, :student_id belongs_to :course, :class_name => 'Course', :foreign_key => :course_id belongs_to :student, :class_name => 'User', :foreign_key => :student_id validates_presence_of :course_id, :student_id validates_uniqueness_of :student_id, :scope => :course_id end