[ROR] 必知必会知识点[持续总结中...]

一、Ruby语言本身

• require、load和include。
  require：形式为require 'active_support/concern'。 请求一个模块，需要不带扩展名的文件名，程序中多次requrie这个模块不会多次装载，ruby会使用内存中的缓存；
  load：形式为require 'active_support/concern.rb'。请求装载一个模块，需要带扩展名，每次执行到load，不管以前是否装载过，ruby都会再次读取此模块；
  include：形式为：include ActiveSupport::Concern。mixin一个模块，使用的是模块的名称而不是文件名，其实和前两个没啥关系，很多时候需要一起使用；
  
  
• 查看一个类的方法。
  methods、public_methods、private_methods、instance_methods、public_instance_methods
  

  irb(main):025:0> Test2.instance_methods
  => [:m1, :to_json, :blank?, :as_json, :acts_like?, :deep_dup, :present?, :duplicable?, :with_options, :html_safe?, :in?, :presence_in, :dclone, :`, :to_yaml, :to_param, :to_query, :instance_values,
   :instance_variable_names, :presence, :pretty_print_cycle, :pretty_print_inspect, :pretty_print, :pretty_print_instance_variables, :require_dependency, :unloadable, :require_or_load, 
  :load_dependency, :try, :try!, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :instance_variable_get, :instance_variables, :instance_variable_set,
   :protected_methods, :private_methods, :public_send, :method, :public_method, :singleton_method, :class_eval, :pretty_inspect, :define_singleton_method, :extend, :suppress_warnings, :to_enum,
   :enum_for, :<=>, :===, :=~, :!~, :eql?, :respond_to?, :gem, :freeze, :inspect, :object_id, :send, :to_s, :display, :class, :nil?, :hash, :dup, :singleton_class, :clone, :then, :itself,
   :yield_self, :untaint, :taint, :tainted?, :trust, :untrust, :untrusted?, :singleton_methods, :frozen?, :methods, :public_methods, :equal?, :!, :==, :instance_exec, :!=, :instance_eval,
   :__id__, :__send__]
  
  

  　　

  # 为了便于查看，可以排一下序
  irb(main):034:0> Test2.instance_methods.sort
  => [:!, :!=, :!~, :<=>, :==, :===, :=~, :__id__, :__send__, :`, :acts_like?, :as_json, :blank?, :class, :class_eval, :clone, :dclone, :deep_dup, :define_singleton_method, :display, :dup, 
  :duplicable?, :enum_for, :eql?, :equal?, :extend, :freeze, :frozen?, :gem, :hash, :html_safe?, :in?, :inspect, :instance_eval, :instance_exec, :instance_of?, :instance_values, 
  :instance_variable_defined?, :instance_variable_get, :instance_variable_names, :instance_variable_set, :instance_variables, :is_a?, :itself, :kind_of?, :load_dependency, :m1, :method,
   :methods, :nil?, :object_id, :presence, :presence_in, :present?, :pretty_inspect, :pretty_print, :pretty_print_cycle, :pretty_print_inspect, :pretty_print_instance_variables, :private_methods, 
  :protected_methods, :public_method, :public_methods, :public_send, :remove_instance_variable, :require_dependency, :require_or_load, :respond_to?, :send, :singleton_class, :singleton_method,
   :singleton_methods, :suppress_warnings, :taint, :tainted?, :tap, :then, :to_enum, :to_json, :to_param, :to_query, :to_s, :to_yaml, :trust, :try, :try!, :unloadable, :untaint, :untrust, 
  :untrusted?, :with_options, :yield_self]
  irb(main):035:0>
  

  　

二、UI视图(ActionView)相关

•  AJAX访问错误引发错误“ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken)” ， 在controller中添加下面命令，跳过校验

  skip_before_action :verify_authenticity_token

三、ActiveRecord 

• 事务操作Transaction，使用ActiveRecord::Base.transaction开始事务，注意的是，内部数据库操作需要使用出错时引发例外的方法（多数以！结尾），这样才能触发事务回滚操作
  

  ActiveRecord::Base.transaction do
     item.save!
     data.save!
  end

• Migration的迁移和回滚操作
  

  # 执行所有未执行的migration
  [ruby@dev project1]$ rails db:migrate
  
  # 查看数据库中migration的当前状态
  [ruby@dev project1]$ rails db:migrate:status
  warning ../package.json: No license field
  
  database: db/development.sqlite3
  
   Status   Migration ID    Migration Name
  --------------------------------------------------
     up     20201124051602  Create active storage tablesactive storage
     up     20201124065250  Create scores
     up     20201124073822  Create score items
  
  # 回滚一个migration，注意表中数据需要自行保存
  [ruby@dev project1]$ rails db:rollback
  [ruby@pms rparanking]$ rails db:rollback
  warning ../package.json: No license field
  == 20201124073822 CreateScoreItems: reverting =================================
  -- remove_index(:score_items, {:name=>"index_score_items_uniqueness"})
     -> 0.0032s
  -- remove_index(:score_items, {:column=>:scorer})
     -> 0.0032s
  -- drop_table(:score_items)
     -> 0.0038s
  == 20201124073822 CreateScoreItems: reverted (0.0135s) ========================
  
  [ruby@pms rparanking]$ rails db:migrate:status
  warning ../package.json: No license field
  
  database: db/development.sqlite3
  
   Status   Migration ID    Migration Name
  --------------------------------------------------
     up     20201124051602  Create active storage tablesactive storage
     up     20201124065250  Create scores
    down    20201124073822  Create score items
  
  [ruby@dev project1]$ rails db:rollback
  warning ../package.json: No license field
  == 20201124065250 CreateScores: reverting =====================================
  -- remove_index(:scores, {:column=>:score_times})
     -> 0.0055s
  -- remove_index(:scores, {:column=>:score})
     -> 0.0031s
  -- remove_index(:scores, {:column=>:pinyin})
     -> 0.0030s
  -- remove_index(:scores, {:column=>:name})
     -> 0.0035s
  -- remove_index(:scores, {:column=>:ename})
     -> 0.0020s
  -- drop_table(:scores)
     -> 0.0014s
  == 20201124065250 CreateScores: reverted (0.0215s) ============================
  
  [ruby@dev project1]$ rails db:migrate:status
  warning ../package.json: No license field
  
  database: db/development.sqlite3
  
   Status   Migration ID    Migration Name
  --------------------------------------------------
     up     20201124051602  Create active storage tablesactive storage
    down    20201124065250  Create scores
    down    20201124073822  Create score items
  
  # 执行db:migrate 回复所有migration状态为up
  # 回滚指定的migration，通过VERSION指定，所谓版本就是db/migrate/下面migration文件名最开始的那一串数字
  [ruby@dev project1]$ rails db:migrate:down VERSION=20201124065250
  # 执行特定的migration，通过VERSION指定，所谓版本就是db/migrate/下面migration文件名最开始的那一串数字
  [ruby@dev project1]$ rails db:migrate:up VERSION=20201124065250

• 命令行生成migration时，复杂数据类型（decimal）的语法 ：
  

  # decimal的单引号时必要的
  rails g model Abc 'price:decimal{5,2}' supplier:references{polymorphic}

• Model中自定义属性（数据库表中不存在），需要序列化为json的需要覆盖as_json
  

   # 扩展json对象，添加pinyin和jianpin属性
    def as_json data    
      if self.respond_to? 'name'
        ps = { pinyin: self.pinyin_name, jianpin: self.jianpin }
        super.merge ps
      end
    end

• ActiveRecord对象 的修改痕迹追踪，记录在此
• Migration中建立联合索引时，一定要指定名称，否则rollback时，会因为找不到生成的索引名称而报错
  

  add_index :score_items, [:score_id, :scorer], name: "index_score_items_uniqueness", unique: true

四、系统相关

• 建立临时文件时，如何指定扩展名。rails建立临时文件很方便，直接Tempfile::newnew(basename="", tmpdir=nil, mode: 0, **options)，但是如何给定一个扩展名呢？原来只需要在第一项参数位置给出一个数组即可，看代码
  
  

  irb(main):001:0> tf = Tempfile::new
  => #<Tempfile:/tmp/20201120-38479-dg7h2v>
  irb(main):002:0> tf.path
  => "/tmp/20201120-38479-dg7h2v"
  irb(main):003:0> tf = Tempfile::new('abc')
  => #<Tempfile:/tmp/abc20201120-38479-abc6ui>
  irb(main):004:0> tf.path
  => "/tmp/abc20201120-38479-abc6ui"
  irb(main):006:0> tf = Tempfile::new(['abc','txt'])
  => #<Tempfile:/tmp/abc20201120-38479-2prba5txt>
  irb(main):007:0> tf.path
  => "/tmp/abc20201120-38479-2prba5txt"
  irb(main):008:0> tf = Tempfile::new(['abc','.txt'])
  => #<Tempfile:/tmp/abc20201120-38479-n6a5j6.txt>
  irb(main):009:0>

    irb(main):020:0> tf = Tempfile.new ['','.jpg']
    => #<Tempfile:/tmp/20201120-38479-qkitzp.jpg>

五、程序发布

•  config/enviroment/production.rb, 静态文件服务打开
  

  config.public_file_server.enabled = true