上一篇：Rails4 升级第一弹： https://ruby-china.org/topics/22280

uninitialized constant Mongoid::MultiParameterAttributes & Mongoid::Versioning

mongoid4 中去掉了 MultiParameterAttributes 和 Versioning，如果想兼容 mongoid3，则需要将 3 中的对应代码拷贝到 4 中

copy mongoid-3 to /lib/mongoid/versiong.rb copy mongoid-3 to /lib/mongoid/multi_parameter_attributes.rb

and add to the requires to initializers/mongoid.rb require 'mongoid/versioning' require 'mongoid/multi_parameter_attributes.rb'

class CouponMongo
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::MultiParameterAttributes
end

https://github.com/mongoid/mongoid/issues/2954

polymorphic 的关联关系在 mongoid4 中去掉了，官方文档给出的实例如下

So where the following would work before:

class Eye
  include Mongoid::Document
  belongs_to :eyeable, polymorphic: true
end

class Face
  include Mongoid::Document
  has_one :left_eye, class_name: "Eye", as: :eyeable
  has_one :right_eye, class_name: "Eye", as: :eyeable
end

This would now need to be modeled as (with the appropriate migration):

class Eye
  include Mongoid::Document
  belongs_to :left_socket, class_name: "Face", inverse_of: :left_eye
  belongs_to :right_socket, class_name: "Face", inverse_of: :right_eye
end

class Face
  include Mongoid::Document
  has_one :left_eye, class_name: "Eye", inverse_of: :left_socket
  has_one :right_eye, class_name: "Eye", inverse_of: :right_socket
end

mongoid polymorphic 扩展：https://ruby-china.org/topics/22508

mongoid4 update_attributes 去掉了 without_protection: true 这个参数

Mass assignment security now mirrors Rails 4's behavior. without_protection option was also removed. attr_accessible class method was removed. Mongoid and Strong parameters should work fine for mass assignment protection.

mongoid3 如果对象不存在某属性，则不进行保存，类似与 strong_parameter 的功能 mongo_class.find_or_initialize_by(id: id).update_attributes(attributes, without_protection: true)

mongoid4 则去掉了这一参数，attributes 需要进行 permit 处理 mongo_class.find_or_initialize_by(id: id).update_attributes(attributes)

set_table_name, set_primary_key.

we should use #table_name = instead of #set_table_name.

otherwise you will get undefined method `set_primary_key' for #Class:0x37132e0

class CmsClientPid < CmsActiveRecord
-  set_table_name "cms_client"
-  set_primary_key :pid
+  self.table_name = "cms_client"
+  self.primary_key = 'pid'
end

rails 最新版本中，在使用 try 调用私有方法的时候，有了一些差异

class User
  include Mongoid::Document

  private
  def say
    puts "hello, world"
  end
end

rails3:

u = User.new
u.try(:say)
==> hello, world

rails4:

u = User.new
u.try(:say)
==> nil

查看详情： https://ruby-china.org/topics/22759

seo friendly_id

Gemfile

gem 'friendly_id', '~> 5.0.0'

edit app/models/user.rb

class User < ActiveRecord::Base
  extend FriendlyId
  friendly_id :name, use: :slugged
end

User.create! name: "Joe Schmoe"

Change User.find to User.friendly.find in your controller

rails3:

User.find(params[:id]) User.find(userid) User.find("username")

rails4: User.friendly.find(params[:id]) User.friendly.find(userid) User.friendly.find("username")

https://github.com/norman/friendly_id/

transaction

transaction 用于回调函数中 rails4 中修改 transaction_include_action?(action) 方法，接收数组，并将方法名改为 transaction_include_any_action?(actions) 同时增加：:set_transaction_state, :has_transactional_callbacks？两个方法

rails3: [:transaction, :add_to_transaction, :with_transaction_returning_status, :remember_transaction_record_state, :clear_transaction_record_state, :restore_transaction_record_state, :transaction_record_state, :transaction_include_action?]

rails4: [:transaction, :add_to_transaction, :with_transaction_returning_status, :remember_transaction_record_state, :clear_transaction_record_state, :restore_transaction_record_state, :transaction_record_state, :transaction_include_any_action?, :set_transaction_state, :has_transactional_callbacks?]

rails3 接受一个参数，rails4 接受一个数组 rails3: transaction_include_action?(action) rails4: transaction_include_any_action?(actions)

rails3:
after_commit :update_profile
def update_profile
  do_something if transaction_include_action?(:update)
end
rails4:
after_commit :update_profile
def update_profile
  do_something if transaction_include_any_action?([:update])
end

mongoid inc

rails3 中 inc 接收两个参数，rails4 则接收一个 hash，可以同时增加多个变量的 count

rails3: skill.inc(:users_count, 1) rails4: skill.inc(users_count: 1)

未完待续。。

博客：http://michael-roshen.iteye.com/blog/2160035 欢迎关注个人微信帐号：ruby 程序员