Ikki xil assotsiatsiyani bir xil ob'ekt bilan qanday baham ko'raman?

Menga tegishli va has_many munosabatlarim bor.

Bola ota-onaga tegishli Ota-onaning ko'p farzandi bor.

Biroq, menda Ota-ona farzand ko'rishning yana bir usuli bor va bu men ota-ona turini guruhlash uchun foydalaniladigan join_table orqali.

Buni qanday qilish haqida mening dahshatli taxminim:

# child.rb

belongs_to :parent
belongs_to :parent_group, :dependent => :destroy
delegate :parent, :to => :parent_group

# parent.rb

has_many :children
has_many :children, through: :parent_groups

E'tibor bering, men ushbu nomlash qoidalaridan foydalanmayman. Bular mening ishimni anonim saqlash uchun o'zgartirildi.

Keyin mening migratsiyalarim quyidagicha ko'rinadi:

class CreateParentGroup < ActiveRecord::Migration
  def self.up
    create_table :parent_groups do |t|
      t.integer :parent_id
      t.timestamps
    end
    add_column :child, :parent_group_id, :integer
  end

Shunday qilib, mening maqsadim shundan iboratki, agar Parent.find(n).children ni yozsam, u ota-ona_guruhi orqali boʻlgan Child obyektlarini va unga bevosita aloqador boʻlgan bolalarni qaytaradi.

Aksincha, agar men Child.find(n).parent ni tanlasam, u ota-ona guruhi orqalimi yoki yo'qmi, o'zining ota-onasini tanlaydi.

Va nihoyat, men parent_groups va ota-onalar to'plamini tanlashim mumkin edi.

Har qanday fikr bormi?


ruby-on-rails associations polymorphic-associations
person Trip    schedule 15.08.2012    source manba

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Birinchidan, agar siz qo'shilish jadvali haqida gapirayotgan bo'lsangiz, menimcha, ushbu jadval uchun sxemani sozlash juda to'g'ri emas. Bu shunday bo'lishi kerak:

class CreateParentGroup < ActiveRecord::Migration
  def self.up
    create_table :parent_groups do |t|
      t.integer :parent_id
      t.integer :child_id
      t.timestamps
    end
  end
end

Shunday qilib, endi sizning stolingiz parent_groups ko'plab ota-onalar uchun ko'plab bolalarni sig'dira oladi.

Modellaringizda assotsiatsiyalaringizni o'rnatishga kelsak: Siz bir xil nomdagi ikkita turli assotsiatsiyani nomlay olmaysiz/kerak emas. Shuning uchun siz bitta modelda bir vaqtning o'zida has_many :children va has_many :children, :through => :parent_groups ni bajara olmaysiz. Sababi, agar siz bolalarga Parent.find(n).children Rails orqali kirsangiz, qaysi assotsiatsiyadan foydalanishni bilmaydi.

Men shunday bir narsa qilardim:

class Parent < AR
  has_many :regular_children, :class_name => 'Child'
  has_many :group_children, :class_name => 'Child', :through => :parent_groups

  # implement a method that combines them both
  def children
    regular_children + group_children
  end
end

class Child < AR
  belongs_to :parent
  belongs_to :parent_group, :dependent => :destroy

  # forget the delegate, otherwise your invoke of Child.find(n).parent always
  # gets delegated to parent_group which is/can be wrong due to data
end

Menimcha, bu ko'proq boradigan yo'l ...

person Vapire    schedule 15.08.2012
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Ajoyib! Katta rahmat Vapire! - person Trip; 15.08.2012