Rails has_many通过查询取决于through表属性

Question

有一些has_many通过查询的问题.

使用这里的例子: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表有一个名为appointment_date的列

如何让特定医生的所有患者在指定日期预约？

Answer 1

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

Date.today可以用任何东西改变,而pysician由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和转发中,您需要添加references(:appointments)到查询中以便在where子句中使用约会.