Rails：麻煩有很多通過關係

我一直有一點難以理解整個有很多概念以及它如何在Rails中工作，我認爲它爲你做腿部工作，因爲我習慣於手動建立關聯。我目前有一個結算系統，我正在嘗試創建一個訂單部分，顯然我的訂單必須有很多產品，所以我已經將數據庫規範化爲第三範式，以便訂單和產品通過另一個表格命名爲訂購產品，此表格包含訂單的ID和產品的ID以及訂購產品的數量。我已經根據我所瞭解的has_Many創建了模型：通過代碼學校教程的Rails，但是我已經完全複製了它的樣子，但是地雷和它們之間必定有某種區別。這是我目前擁有的模型文件：Rails：麻煩有很多通過關係

訂貨型號：

class Order < ActiveRecord::Base 
    attr_accessible :ClientID, :OrderTotal 
    has_many :orderedproducts 
    has_many :products, through: :orderedproducts, :source => :product 

end

訂購的產品型號：

class Orderedproduct < ActiveRecord::Base 
    attr_accessible :OrderID, :ProductID, :QuantityOrdered 
    belongs_to :order 
    belongs_to :product 
end

產品型號：

class Product < ActiveRecord::Base 
    #This line makes these elements accessible outside of the class. 
    attr_accessible :ProductName, :ProductPrice, :ProductQuantity, :ProductSupplier 

    has_many :orderedproducts 
    has_many :orders, through: :orderedproducts, :source => :order 

    #These attributes ensure that the data entered for each element is valid and present. 
    validates_presence_of :ProductName 
    validates_presence_of :ProductPrice 
    validates_numericality_of :ProductPrice 
    validates_presence_of :ProductQuantity 
    validates_numericality_of :ProductQuantity 
    validates_presence_of :ProductSupplier 

end

我添加源屬性因爲我在控制檯中發現錯誤，提示我應該將源屬性添加到h as_many：通過線路。這是我收到的控制檯中的錯誤，當我嘗試將產品添加到訂單：

irb(main):017:0> order.products = Product.find(4) 
    Product Load (0.3ms) SELECT `products`.* FROM `products` WHERE `products`.`id` = 4 LIMIT 1 
ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :ProductID in model Orderedproduct. Try 'has_many :products, :through => :orderedproducts, :source => <name>'. Is it one of :order or :product? 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/reflection.rb:509:in `check_validity!' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations/association.rb:26:in `initialize' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:24:in `initialize' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations/has_many_through_association.rb:10:in `initialize' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations.rb:160:in `new' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations.rb:160:in `association' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/activerecord-3.2.13/lib/active_record/associations/builder/association.rb:51:in `block in define_writers' 
     from (irb):17 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start' 
     from /usr/local/rvm/gems/ruby-2.0.0-p0/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>' 
     from script/rails:6:in `require' 
     from script/rails:6:in `<main>'

來源

2013-05-11 Conner Stephen McCabe

由於訂單的has_many產品，你從Rails中#products方法，而不是一個#product方法。

你可以做的是使用訂單實例來創建一個相關OrderedProducts和產品添加到該實例。

order = Order.new 
ordered_product = order.ordered_products.build 
ordered_product.product = Product.find(4)

與訂購#product方法的問題是有，就是要集合，所以你的代碼來知道你的意思是哪一個？

來源

2013-05-11 13:39:01 Michael

我使用的是錯誤的數組運算符，應該是運算符而不是=運算符，因爲我在數組中添加了一個元素。

來源

2013-05-11 13:44:06

在這種情況下，它的產物=方法;訂單沒有'產品'，它有很多'產品'。

您可以：

order.products << some_product

的首字母大寫，不幸的是，也是一個問題。 Order和Product的關聯將分別查找order_id或product_id，並且不會找到它們。解決方案將把列名更改爲snake_case，或者添加：foreign_key => ...選項。

來源

2013-05-11 14:13:26 philcrissman

Rails：麻煩有很多通過關係

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