Objects inheritances

Background jobs

Sidekiq

Redis and multiple threaded process

  while(!empty(queue)) {
         = get(queue); //从任务队列中取一个(涉及加锁等)
        q->callback(); //执行该任务
    }

Syntax
- lambda
- yield
- respond_to
- send
- <=>
  - return 1,0, -1
- - before array
    - splat operator: split an array into a list of arguments
- array << obj
  - append obj to new arry
block {} do end
- Block is not object
- use yield pass block
Proc
- Proc is object
- greeting = Proc.new { puts "hello, world" } greeting.call
Module
- Can't be new
- include
- can't extend
Class

- ORM
	- Active record
	- Mongoid
- Websocket
- Assets pipeline
- Rails console