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ActiveRecord Store 使用介绍 at 2017年03月08日

，的确很坑，得定义 permissions= 的行为才行

ActiveRecord Store 使用介绍 at 2017年03月08日

哦，这个用法没试过，回头试试。我想当然以为 serialize 要求数据库类型必须为 string 了

不过搜了下 5.0 的 doc，貌似不推荐这种情况用 serialize 了

http://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/Serialization/ClassMethods.html

If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically. The serialization is done through YAML. If class_name is specified, the serialized object must be of that class on assignment and retrieval. Otherwise SerializationTypeMismatch will be raised.

Empty objects as {}, in the case of Hash, or [], in the case of Array, will always be persisted as null.

Keep in mind that database adapters handle certain serialization tasks for you. For instance: json and jsonb types in PostgreSQL will be converted between JSON object/array syntax and Ruby Hash or Array objects transparently. There is no need to use serialize in this case.

For more complex cases, such as conversion to or from your application domain objects, consider using the ActiveRecord::Attributes API.

ActiveRecord Store 使用介绍 at 2017年03月08日

这个功能只要 orm 层可以反射为 hash 就可以实现了，使用 hstore 或者 serialize 在这个场景并没有啥区别，但是我的意思是 hstore 的好处是，它是 pg 原生支持的类型，可以做

SELECT
 sum (attrs -> 'like_count') As total_likes
FROM
 posts;
GROUP BY xxx

这种级别的操作，所以如果数据库层面原生支持 json，最好直接用原生类型，而不是 serialize。

ActiveRecord Store 使用介绍 at 2017年03月08日

是不冲突，效率低功能少呀

ActiveRecord Store 使用介绍 at 2017年03月08日

postgre 原生的数据类型支持索引，支持数据库级别的操作，能用原生就用原生的 active record 的方案是在数据库不支持的前提下没办法的方案。

基于 Rails 5 的 B2C 电商开源项目 at 2017年03月03日

比如下面 payment 里面这段代码

def self.create_from_orders! user, *orders
  orders.flatten!

  payment = nil
  transaction do
    payment = user.payments.create!(
      total_money: orders.sum(&:total_money)
    )

    orders.each do |order|
      if order.is_paid?
        raise "order #{order.order_no} has already paid"
      end

      order.payment = payment
      order.save!
    end
  end

既没有看到使用悲观锁，订单上也没有创建乐观锁，方法内也并没有分布式锁做排他调用保证

create_table "orders", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
  t.integer  "user_id"
  t.integer  "product_id"
  t.integer  "address_id"
  t.string   "order_no"
  t.integer  "amount"
  t.decimal  "total_money", precision: 10, scale: 2
  t.datetime "payment_at"
  t.datetime "created_at",                                               null: false
  t.datetime "updated_at",                                               null: false
  t.integer  "payment_id"
  t.string   "status",                               default: "initial"
  t.index ["order_no"], name: "index_orders_on_order_no", unique: true, using: :btree
  t.index ["payment_id"], name: "index_orders_on_payment_id", using: :btree
  t.index ["user_id"], name: "index_orders_on_user_id", using: :btree
end