ruby-on-rails - ruby 有很多 through 两种模型

Question

问题:在 enrollment.attendances.count(:id) 中，注册必须只能访问与 student_id 和 course_id 匹配的那些出勤率。

这是我的 4 db 依赖项:

class Enrollment < ActiveRecord::Base
  belongs_to :course
  belongs_to :student
  has_many :attendances, through: :client
  has_many :attendances, through: :course

,

class Student < ActiveRecord::Base
  has_many :enrollments
  has_many :attendances

,

class Course < ActiveRecord::Base
  has_many :enrollments
  has_many :attendances

,

class Attendance < ActiveRecord::Base
  belongs_to :student
  belongs_to :course

,

模型依赖的架构:

Answer 1

首先可以通过student_id和course_id从Enrollment中找到object

然后检查是否出席 然后你可以找到count。

@enrolls = Enrollment.where(course_id: id1, student_id: id2)
@enrolls.each do |enrol|
   if enrol.attended == true
       puts Attendance.where(course_id: id1, student_id: id2).count
   end
end