ROR汇集---aasm

aasm的工作原理其实是状态机，与state_machine基本一致，关于state_machine的部分信息可以参考：http://flyingzl.javaeye.com/blog/362207

 

工作原理图：

 

 

 

以下内容转自：http://github.com/rubyist/aasm/tree/master

 

AASM - Ruby state machines

This package contains AASM, a library for adding finite state machines to Ruby classes.

AASM started as the acts_as_state_machine plugin but has evolved into a more generic library that no longer targets only ActiveRecord models.

AASM has the following features:

• States
• Machines
• Events
• Transitions

Download

The latest AASM can currently be pulled from the git repository on github.

• github.com/rubyist/aasm/tree/master

Installation

From GitHub hosted gems

  % sudo gem sources -a http://gems.github.com # (you only need to do this once)
  % sudo gem install rubyist-aasm

Building your own gems

  % rake gem
  % sudo gem install pkg/aasm-2.1.gem

Simple Example

Here’s a quick example highlighting some of the features.

  class Conversation
    include AASM

    aasm_initial_state :unread

    aasm_state :unread
    aasm_state :read
    aasm_state :closed

    aasm_event :view do
      transitions :to => :read, :from => [:unread]
    end

    aasm_event :close do
      transitions :to => :closed, :from => [:read, :unread]
    end
  end
 

A Slightly More Complex Example

This example uses a few of the more complex features available.

  class Relationship
    include AASM

    aasm_initial_state Proc.new { |relationship| relationship.strictly_for_fun? ? :intimate : :dating }

    aasm_state :dating,   :enter => :make_happy,        :exit => :make_depressed
    aasm_state :intimate, :enter => :make_very_happy,   :exit => :never_speak_again
    aasm_state :married,  :enter => :give_up_intimacy,  :exit => :buy_exotic_car_and_wear_a_combover

    aasm_event :get_intimate do
      transitions :to => :intimate, :from => [:dating], :guard => :drunk?
    end

    aasm_event :get_married do
      transitions :to => :married, :from => [:dating, :intimate], :guard => :willing_to_give_up_manhood?
    end

    def strictly_for_fun?; end
    def drunk?; end
    def willing_to_give_up_manhood?; end
    def make_happy; end
    def make_depressed; end
    def make_very_happy; end
    def never_speak_again; end
    def give_up_intimacy; end
    def buy_exotic_car_and_wear_a_combover; end
  end

 

当状态机建立好后，我们来探讨一下它的用法：

1、与数据库关联起来。

include AASM 
aasm_column :aasm_state
aasm_initial_state :pending 

 如上所示，我们通过aasm_column把状态机与数据库表的aasm_state字段关联起来，当我们调用状态机事件时，aasm_state的值会发生相应的变化。

2、可以定义状态机的初始状态（aasm_initial_state），当插入数据时，如果不干预状态机，它会自动获取一个初始状态（预先定义的），并保存到数据库表。

3、Model.even与Model.even!的区别。

先看以下代码：

class Book < ActiveRecord::Base
  # ... 

  aasm_event :close do
    transitions :to => :closed, :from => [:opened]
  end

  # ...
end
 

If you call the bang! form of the transition event method, the state will persist.

So calling book.close will set the state to closed, but will not automatically save. Calling book.close! will set the 

state *and* automatically save the AR object.

4、其它用法：

class ChetanPatil
  include AASM
  aasm_initial_state :sleeping
  aasm_state :sleeping
  aasm_state :showering
  aasm_state :working
  aasm_state :dating
 
  aasm_event :wakeup do
    transitions :from => :sleeping, :to => [:showering, :working]
  end
 
  aasm_event :dress do
    transitions :from => :sleeping, :to => :working, :on_transition => :wear_clothes
    transitions :from => :showering, :to => [:working, :dating], :on_transition => Proc.new { |obj, *args| obj.wear_clothes(*args) }
  end
 
  def wear_clothes(shirt_color, trouser_type)
  end
end

#invoke
cp = ChetanPatil.new
cp.wakeup! :showering 

参考：http://github.com/rubyist/aasm/blob/dfc2874972daf601f3eeb4cd2bff589290cc2521/spec/unit/aasm_spec.rb

注意：

倘若状态机跳转不符合要求。如事件wakeup触发的状态是从sleeping到showering,working的，但如果调用wakeup时，状态机当前的状态不为sleeping时，

就会出现异常。所以对于这些异常要注意捕获和处理。