如何避免通过关联在has_many连接表中创建重复记录？

Question

我有两个型号Physician，Patient和联接模型Appointment和协会就像如下：

class Physician < ActiveRecord::Base 
    has_many :appointments 
    has_many :patients, through: :appointments 
    accepts_nested_attributes_for :patients 
end 

class Patient < ActiveRecord::Base 
    has_many :appointments 
    has_many :physicians, through: :appointments 
    accepts_nested_attributes_for :appointments 
end 

class Appointment < ActiveRecord::Base 
    belongs_to :physician 
    belongs_to :patient 
end 

我想在appointment表更新appoinment_data时，有在appointment表中的新 条目。

所以在轨控制台：

a = Physician.last 
#<Physician id: 1, name: "Hamza", address: "Pune", created_at: "2017-02-22 07:07:10", updated_at: "2017-02-22 07:07:10"> 

a.update(patients_attributes: [{ name: 'Prajakta', disease: 'Fever', appointments_attributes: [{appointment_data: DateTime.now}]}]) 
    (0.7ms) BEGIN 
    SQL (0.9ms) INSERT INTO "patients" ("name", "disease", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["name", "Prajakta"], ["disease", "Fever"], ["created_at", "2017-02-22 08:30:22.321863"], ["updated_at", "2017-02-22 08:30:22.321863"]] 
    SQL (0.8ms) INSERT INTO "appointments" ("appointment_data", "patient_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["appointment_data", "2017-02-22 08:30:22.311198"], ["patient_id", 5], ["created_at", "2017-02-22 08:30:22.326373"], ["updated_at", "2017-02-22 08:30:22.326373"]] 
    SQL (0.9ms) INSERT INTO "appointments" ("physician_id", "patient_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["physician_id", 1], ["patient_id", 5], ["created_at", "2017-02-22 08:30:22.333624"], ["updated_at", "2017-02-22 08:30:22.333624"]] 
    (1.2ms) COMMIT 
=> true 

它在appointment表中创建两个records。 appointment_data和patient_id的一条记录。其他与physician_id和patient_id。

我在这里失踪了什么？

Answer 1

我找到了一个解决方法，放置accepts_nested_attributes_for。我现在联想是这样的：

class Physician < ActiveRecord::Base 
    has_many :appointments 
    has_many :patients, through: :appointments 
    accepts_nested_attributes_for :appointments 
end 

class Patient < ActiveRecord::Base 
    has_many :appointments 
    has_many :physicians, through: :appointments 
end 

class Appointment < ActiveRecord::Base 
    belongs_to :physician 
    belongs_to :patient 
    accepts_nested_attributes_for :patients 
end 

我在控制台这样做：

a = Physician.last 
a.update(appointment_attributes: [{appointment_data: DateTime.now, patient_attributes: {name: 'Rajesh', disease: 'fever'}}]) 

它现在在appointments表只创建一个记录。