如何在连接模型上编写“范围”？

Question

假设我有这些模型：Physician通过Patients有很多Appointments。

class Physician < ActiveRecord::Base
  has_many :appointments
  has_many :patients, :through => :appointments
end
 
class Appointment < ActiveRecord::Base
  belongs_to :physician
  belongs_to :patient
end
 
class Patient < ActiveRecord::Base
  has_many :appointments
  has_many :physicians, :through => :appointments
end

我想写一个范围或类似的东西，这样我就可以找到一位确认任命的医生的所有患者。

最常用的方法是什么？

Answer 1

使用has_many：通过关联：

执行此操作

has_many :confirmed_patients, :through => :appointments, :source => :patient, :class_name => 'Patient', :conditions => { :confirmed => true }