Destroying a user should remove it from their courses

Author: Jordan Byron

app/models/course_membership.rb

@@ -11,7 +11,7 @@ class CourseMembership < ActiveRecord::Base
   private
 
   def destory_assignment_submissions
-    student.assignment_submissions.includes(:assignment).
+    Assignment::Submission.where(:user_id => user_id).includes(:assignment).
       where(["assignments.course_id = ?", self.course_id]).each do |sub|
         sub.delete
       end

app/models/user.rb

@@ -3,7 +3,7 @@ class User < ActiveRecord::Base
   has_many :chat_channel_memberships, :class_name => "Chat::ChannelMembership"
   has_many :chat_channels, :through => :chat_channel_memberships, :source => :channel, :class_name => "Chat::Channel"
 
-  has_many :course_memberships
+  has_many :course_memberships, :dependent => :destroy
   has_many :courses, :through => :course_memberships
 
   has_many :assignment_submissions, :class_name => "Assignment::Submission"