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_stateaasm_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)  endend#invokecp = ChetanPatil.newcp.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。