调整

app/models/course.rb

@@ -82,6 +82,7 @@ class Course < ApplicationRecord
   scope :by_keywords, lambda { |keywords|
     where("name LIKE ?", "%#{keywords.split(" ").join('|')}%") unless keywords.blank?
   }
+  scope :started,  -> { where("start_date is null or start_date <= '#{Date.today}'") }
 
   acts_as_taggable
 

app/services/users/course_service.rb

@@ -23,11 +23,11 @@ class Users::CourseService
   def category_scope_courses
     case params[:category]
     when 'study' then
-      user.as_student_courses
+      user.as_student_courses.started
     when 'manage' then
       user.manage_courses
     else
-      ids = user.as_student_courses.pluck(:id) + user.manage_courses.pluck(:id)
+      ids = user.as_student_courses.started.pluck(:id) + user.manage_courses.pluck(:id)
       Course.where(id: ids)
     end
   end