ruby-on-rails - rails : Has_many through query depending on the through table attribute

Question

has_many 通过查询遇到一些问题。

使用此处的示例:http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association

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

Appointment 表有一列名为 约会日期

我如何从特定医生那里获得在给定日期预约的所有患者？

Answer 1

Patient.includes(:physicians, :appointments).where('physicians.id = ? AND appointments.appointment_date = ?', <id or ids array>, Date.today)

其中 Date.today 可以用任何东西更改，并且医生由一个 id 或一组 id 指定。

你也可以这样做:

physician = Physician.find(id)
patients = physician.patients.includes(:appointments).where('appointments.appointment_date  = ?', some_date)

编辑:

在 Rails 4 及更高版本中，您需要添加 references(:appointments)到查询以在 where 子句中使用约会。