has_many,class_name,foreign_key,include?,through,source

has_many的使用技巧

+ def main_manager

+    creator

+  end

+

   module UserMethods

     def self.included(base)

-      base.has_many :course_subjects

+      base.has_many :created_course_subjects, :class_name => "CourseSubject",

+                    :foreign_key => :creator_id

     end

   end

     def add_course(course, user)

-      return if _check_user(user) || self.course_subject_courses.by_course(course).first

+      return if !self.is_manager?(user) || self.courses.include?(course)

       self.course_subject_courses.create(:course => course, :manager_id => user.id)

     end

     def remove_course(course, user)

-      return if _check_user(user)

-      course_subject_course = self.course_subject_courses.by_course(course).first

-      course_subject_course.destroy if course_subject_course

+      return if !self.is_manager?(user)

+      self.course_subject_courses.by_course(course).destroy_all

+    end

+

+    def is_manager?(user)

+      self.main_manager == user || self.secondary_managers.include?(user)

     end

-    private

-      def _check_user(user)

-        course_subject_course       = self.creator.id == user.id

-        course_subject_managership  = self.course_subject_managerships.by_user(user).first

-        return true if !(course_subject_course || course_subject_managership)

-      end

   end

   def user_check

     if self.user_id == self.course_subject.creator_id

-      errors.add :base, 'course_subject_managerships.user_id == course_subject.creator_id' 

+      errors.add :base, '不能把主管理员设置为副管理员'

     end

   end

     def self.included(base)

       base.has_many :course_subject_managerships

-      base.has_many :managers, :through => :course_subject_managerships, :source => :user

+      base.has_many :secondary_managers, :through => :course_subject_managerships, :source => :user

     end

     def remove_manager(user)

-      course_subject_managership = self.course_subject_managerships.by_user(user).first

-      course_subject_managership.destroy if course_subject_managership

+      self.course_subject_managerships.by_user(user).destroy_all

     end

     def self.included(base)

       base.has_many :course_subject_managerships

        # user作为副管理员的课程主题

-      base.has_many :course_subjects, :through => :course_subject_managerships

+      base.has_many :manage_course_subjects, :through => :course_subject_managerships, :source => :course_subject

     end