如果尚未在Rails中进行预约，则将患者添加到医师模型中4

Question

考虑以下模型：

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

目的 ：

1. 如果尚不存在，请创建一个患者。
2. 将患者添加到特定医师（如果尚不存在）

我想，我可以用两种方法做到这一点：

方法1

physician = Physician.find(physician_id)
unless Patient.where(email: email).empty?
  record = physician.patients.create email: email
else
#Patient already exist, just add them to appointment
  record = Patient.where(email: email)
  physician.patients << record
end

方法二

physician = Physician.find(physician_id)
record = Patient.find_or_create_by(email: email)
# avoid overhead of SQL JOINS, use simple SELECT/CREATE
if Appointment.where(physician_id: physician_id).where(patient_id: record.id).empty?
   Appointment.create physician_id: physician.id, patient_id: record.id
end

现在，从以上两种方法中选择哪一种更好？ 此外，在性能方面，还有没有比上一年更好的方法了？

Answer 1

选项3呢？

physician = Physician.find(physician_id)
unless physician.patients.where(email: email).exists?
  patient = Patient.find_or_create_by(email: email)
  physician.appointments.create(patient: patient)
end

如果患者已经预约了该医生，这将避免不必要地调用find_or_create_by 。

记录在案，调用model.association.create(...)将不执行任何联接。 它对表示关联的ActiveRelation对象起作用，并且只会触发INSERT语句。 但是，建议的方法1还有其他一些技术问题，方法2不必要地冗长。