如何设置这个 has_many 关联？

Question

所以我有一个PortStock 模型，它具有action: buy 和action: sell 枚举属性。每个PortStock 可以是position: open 或position: closed（也是枚举值）。

然而，关闭一个PortStock 是另一个PortStock（即一个PortStock.sell 关闭一个PortStock.buy）。

所以我创建了一个名为ClosedPositions 的连接模型，基本上我想要做的是记录一个PortStock 关闭另一个的元数据。

这是我的ClosedPosition.rb 模型的架构和模型：

# == Schema Information
#
# Table name: closed_positions
#
#  id             :bigint(8)        not null, primary key
#  closer_id      :integer
#  closed_id      :integer
#  num_units      :integer
#  closed_price   :float
#  dollar_change  :float
#  percent_change :float
#  ticker         :string
#  created_at     :datetime         not null
#  updated_at     :datetime         not null
#

class ClosedPosition < ApplicationRecord
  belongs_to :closer, class_name: "PortStock", foreign_key: "closer_id"
  belongs_to :closed, class_name: "PortStock", foreign_key: "closed_id" 
end

在我的PortStock 模型上，我有一个简单的has_many :closed_positions。

但是，当我尝试将closed_position 添加到现有的port_stock 对象时，我收到unknown attribute port_stock_id 错误。

[27] pry(main)> closer = PortStock.find(8)
  PortStock Load (0.4ms)  SELECT  "port_stocks".* FROM "port_stocks" WHERE "port_stocks"."id" = $1 LIMIT $2  [["id", 8], ["LIMIT", 1]]
=> #<PortStock:0x00007fc951a47c30
 id: 8,
 portfolio_id: 1,
 stock_id: 84,
 volume: 250,
 purchase_price: 4.1,
 current_price: 4.0,
 percent_change: -2.43902439024389,
 created_at: Tue, 12 Jun 2018 00:46:09 UTC +00:00,
 updated_at: Tue, 12 Jun 2018 00:46:09 UTC +00:00,
 current_value: 1000.0,
 dollar_change: -24.9999999999999,
 total_spend: 1025.0,
 bought_on: Sat, 09 Jun 2018 00:00:00 UTC +00:00,
 action: "sell",
 position: "open",
 ticker: "KEY">

[28] pry(main)> closed = PortStock.find(5)
  PortStock Load (0.7ms)  SELECT  "port_stocks".* FROM "port_stocks" WHERE "port_stocks"."id" = $1 LIMIT $2  [["id", 5], ["LIMIT", 1]]
=> #<PortStock:0x00007fc951a55858
 id: 5,
 portfolio_id: 1,
 stock_id: 84,
 volume: 250,
 purchase_price: 4.1,
 current_price: 4.0,
 percent_change: -2.43902439024389,
 created_at: Mon, 11 Jun 2018 03:11:10 UTC +00:00,
 updated_at: Mon, 11 Jun 2018 23:28:30 UTC +00:00,
 current_value: 1000.0,
 dollar_change: -24.9999999999999,
 total_spend: 1025.0,
 bought_on: Sat, 09 Jun 2018 00:00:00 UTC +00:00,
 action: "buy",
 position: "open",
 ticker: "KEY">

[34] pry(main)> closer.closed_positions.create(closed: closed, num_units: closer.volume, closed_price: closed.stock.price, ticker: closed.ticker)
  Stock Load (1.7ms)  SELECT  "stocks".* FROM "stocks" WHERE "stocks"."id" = $1 LIMIT $2  [["id", 84], ["LIMIT", 1]]
   (0.2ms)  BEGIN
   (0.3ms)  ROLLBACK
ActiveModel::UnknownAttributeError: unknown attribute 'port_stock_id' for ClosedPosition.
from /.rvm/rubies/ruby-2.5.1/lib/ruby/gems/2.5.0/gems/activemodel-5.2.0/lib/active_model/attribute_assignment.rb:53:in `_assign_attribute'
[35] pry(main)> closer.closed_positions.create(closed_id: closed.id, num_units: closer.volume, closed_price: closed.stock.price, ticker: closed.ticker)
   (0.2ms)  BEGIN
   (0.3ms)  ROLLBACK
ActiveModel::UnknownAttributeError: unknown attribute 'port_stock_id' for ClosedPosition.
from /.rvm/rubies/ruby-2.5.1/lib/ruby/gems/2.5.0/gems/activemodel-5.2.0/lib/active_model/attribute_assignment.rb:53:in `_assign_attribute'

我该如何解决这个问题？

我接近这个了吗？我可能弄乱了关联语法和逻辑。

Answer 1

当您尝试创建 closed_positions 记录时，ActiveRecord 假定存在外键 port_stock_id，在这种情况下不存在。所以尝试下面的解决方案添加有可能的关联。我添加了两者（我不知道它在当前上下文中的相关性）。这样您就可以创建关联的记录。

class PortStock < ApplicationRecord has_many :closed_stock_positions, foreign_key: 'closed_id', class_name: 'ClosedPosition' has_many :closer_stock_positions, foreign_key: 'closer_id', class_name: 'ClosedPosition' end

Answer 2

ActiveRecord 抱怨的是我的ClosedPosition 模型上没有port_stock_id 列。

所以，我只是将closed_id 列重命名为port_stock_id，然后我将ClosedPosition 模型中的关联从：

class ClosedPosition < ApplicationRecord
  belongs_to :closed, class_name: "PortStock", foreign_key: "closed_id" 
end

收件人：

class ClosedPosition < ApplicationRecord
  belongs_to :closed, class_name: "PortStock", foreign_key: "port_stock_id" 
end

现在就像一个魅力。