mysql - 导轨 : Trouble with has many through relationships

Question

我在理解整体概念及其在 Rails 中的工作原理方面遇到了一些困难，我认为它可以为您完成一些工作，因为我习惯于手动构建关联。我目前有一个计费系统，我正在尝试创建一个订单部分，显然我的订单必须有许多产品，因此我已将数据库标准化为第三范式，以便订单和产品通过另一个链接名为订购产品的表，该表包含订单 ID 和产品 ID，以及订购产品的数量。我根据我所知道的 has_Many :through 通过 Code School 教程在 Rails 中创建了模型，但是我已经完全复制了他们的模型，但是我的模型和他们的模型之间肯定存在某种差异。这是我当前拥有的模型文件:

订购型号:

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

end

订购的产品型号:

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

产品型号:

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

我添加了源属性，因为我在控制台中收到错误，建议我应该将源属性添加到 has_many :through 行。这是当我尝试将产品添加到订单时在控制台中收到的错误:

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>'

Answer 1

在本例中，它是product=方法；订单没有“产品”，它有很多“产品”。

你可以:

order.products << some_product

不幸的是，CamelCase 也是一个问题。 Order 和 Product 的关联将分别查找 order_id 或 Product_id，但不会找到它们。解决方案是将列名称更改为 Snake_case，或添加 :foreign_key => ... 选项。