驗證獨特的範圍

Question

的Rails 4.2和PostgreSQL 9.3

型號關係是：

class Nesting < ActiveRecord::Base 
    belongs_to :product 
    belongs_to :configurator, touch: true 

    validates :product_id, uniqueness: { scope: :configurator } 
end 

class Configurator < ActiveRecord::Base 
    has_many :nestings, dependent: :destroy 
    has_many :products, through: :nestings 

    accepts_nested_attributes_for :nestings, reject_if: :all_blank, allow_destroy: true 
end 

的情況，我創建配置與產品foo，然後嘗試更新，以增加產品foo工作正常。我收到錯誤has_already_taken。

但是，當我一次添加兩個相同的產品驗證不起作用。 Configurator範圍內Nesting型號的product_id的唯一性如何驗證？

我的意見是非常基礎的：

= simple_form_for @configurator, remote: true do |f| 
    = f.simple_fields_for :nestings do |nesting| 
    = render 'nesting_fields', f: nesting 
    = link_to_add_association 'add product', f, :nestings, class: 'btn btn-default' 
    = f.button :submit 

_nesting_fields.html.slim

.nested-fields 
    .form-inline 
    = f.association :product, collection: @products 
    = link_to_remove_association f, class: 'btn btn-default' do 
     .glyphicon.glyphicon-remove 

一個快速的解決方案是在控制器動作參數檢查的product_id's唯一性。但我不喜歡驗證發生在控制器操作中的想法。

Answer 1

在Configurator上添加validates_associated可能會有所幫助，但我會爲Nesting添加唯一性約束。在遷移：

class AddUniqueIndexToNesting < ActiveRecord::Migration 
    def change 
    add_index :nestings, [:configurator_id, :product_id], unique: true 
    end 
end 

另見：

Rails 3: Uniqueness validation for nested fields_for

Rails - Validate Nested Attributes Uniqueness with scope parent of parent

https://github.com/rails/rails/issues/1572