Question

我有一个Contract模型，每个模型有两个Payment（prepayment和second_payment）。

我知道一种可行的方法可能如下：

class Contract < ActiveRecord::Base
  belongs_to :prepayment, :class_name => "Payment"
  belongs_to :second_payment, :class_name => "Payment"
end


## Schema 
create_table "contracts" do |t|
  t.integer  "prepayment_id"
  t.integer  "second_payment_id"
end

但从逻辑上讲，对于属于contract的{{1}}或者payment有合同，这听起来不合适。应该反过来。

建立这种关系的最佳做法是什么？

Answer 1

我宁愿使用支付模式关联正常，也可以在支付中添加一个类别，“预付款”可以是0，“付款”可以是1。通过这种方式，您可以通过添加其他类别来进行其他类型的付款，并且您不需要每次都修改关联。

class Contract < ActiveRecord::Base
  has_many :payments
end

class Payment < ActiveRecord::Base
  enum category: [ :payment, :prepayment ]
end

## Schema 
create_table "prepayment" do |t|
  t.integer  "category"
end

Answer 2

逻辑方法是使用这个（简单实现）：

class Contract < ActiveRecord::Base
  has_many :payment_transactions, as: :transactionable
end

class PaymentTransaction < ActiveRecord::Base
  belongs_to :transactionable, polymorphic: true
end

对于PaymentTransaction，您可以使用枚举字段：

enum payment_type: [:first_income, :expense]

Answer 3

我这样做：

#app/models/contract.rb
class Contract < ActiveRecord::Base
   has_many :payments, -> { where(category: [0,1]) } #-> only returns the payments where category is "prepayment" or "secondary_payment"
end

#app/models/payment.rb
class Payment < ActiveRecord::Base
   belongs_to :contract
   enum category: [:prepayment, :secondary_payment]

   validates :category, uniqueness: { scope: :contract_id } #-> only one of each category per contract

   scope :pre,       -> { find_by category: 0 }
   scope :secondary, -> { find_by category: 1 }
end

这样，您就可以使用以下内容：

@contract = Contract.find(1)

@contract.payments.pre
@contract.payments.secondary

在Rails中建模`has_two`关系的最佳方法是什么？

3 个答案: