ruby-on-rails - Rails 4 STI 继承

Question

我像这样成功地使用单表继承:

class Transaction < ActiveRecord::Base
    belongs_to :order
end

class Purchase < Transaction
end

class Refund < Transaction
end

缩写/简化的 PurchaseController 如下所示:

class PurchaseController < TransactionController
  def new
    @transaction = @order.purchases.new(type: type)
  end

  def create
    @transaction = @order.purchases.new secure_params
    if @transaction.save
      redirect_to @order
    else
      render :new
    end
  end
end

缩略/简化的购买模型如下所示:

class Purchase < Transaction
  attr_accessor :cc_number, :cc_expiry, :cc_csv
end

我想做的是购买的不同变体，例如现金购买和支票购买。问题是我不确定如何调用该变体的模型。

例如:

class Cash < Purchase
  attr_accessor :receipt_no
end

class CashController < TransactionController
  def new
    # This will use the Purchase.rb model so that's no good because I need the Cash.rb model attributes
    @transaction = @order.purchases.new(type: type)

    # This gives me the following error:
    # ActiveRecord::SubclassNotFound: Invalid single-table inheritance type: Purchase is not a subclass of Cash
    @transaction = Cash.new(type: 'Purchase', order: @order.id)
  end
end

Answer 1

我不确定为什么它对你不起作用，这对我来说很好:

@order.purchases.new(type: "Cash") # returns a new Cash instance

如果您准备保存，您也可以将新的 Cash 推送给协会:

@order.purchases << Cash.new

或者你可以在Order中定义一个单独的关联:

class Order < ActiveRecord::Base
  has_many :cashes
end

@order.cashes.new # returns a new Cash instance