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我正在使用 Transitions gem 在我的模型设置中创建一个状态机，如下所示：

require 'transitions'

class Batch < ActiveRecord::Base
  include Transitions

  state_machine do
    state :pending
    state :completed


    event :change_state do 
      transitions :to => :completed, :from => [:pending] 
    end

  end


end

我想查询模型以获取具有特定状态的所有记录，例如：

Batch.where :current_state => :pending

但这似乎不起作用，而且我很难找到这方面的文档。有谁知道如何做到这一点？（我敢肯定它似乎无法找到它）提前谢谢！

编辑

运行 tail -n development.log 给我：

ActionView::Template::Error (SQLite3::SQLException: no such column: batches.current_state: SELECT "batches".* FROM "batches" WHERE "batches"."user_id" = 1 AND "batches"."current_state" = 'pending'):
    3: <%= link_to 'New Batch', new_batch_path %>
    4: 
    5:                                                                      
    6: <% unless @pending_batches.length < 1 %>
    7:  You have <%= @pending_batches.length %> batches pending on these urls:
    8:  <% @pending_batches.each do |batch| %>
    9:      <%= batch.url %>        
  app/views/batches/index.html.erb:6:in `_app_views_batches_index_html_erb___355556540_17724200__911230187'
  app/controllers/batches_controller.rb:8:in `index'

Rendered /Users/dshipper/.rvm/gems/ruby-1.9.2-p180@artsicle/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.5ms)
  Batch Load (0.5ms)  SELECT "batches".* FROM "batches" WHERE "batches"."user_id" = 1 AND "batches"."current_state" = 'pending'
SQLite3::SQLException: no such column: batches.current_state: SELECT "batches".* FROM "batches" WHERE "batches"."user_id" = 1 AND "batches"."current_state" = 'pending'
Rendered /Users/dshipper/.rvm/gems/ruby-1.9.2-p180@artsicle/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (6.6ms)
Rendered /Users/dshipper/.rvm/gems/ruby-1.9.2-p180@artsicle/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (16.1ms)
  SQL (0.2ms)   SELECT name
 FROM sqlite_master
 WHERE type = 'table' AND NOT name = 'sqlite_sequence'

  Batch Load (0.3ms)  SELECT "batches".* FROM "batches" HAVING "batches"."current_state" = 'pending'
SQLite3::SQLException: a GROUP BY clause is required before HAVING: SELECT "batches".* FROM "batches" HAVING "batches"."current_state" = 'pending'

运行 grep 'current_state db/schema.rb' 不返回任何结果。我希望虽然没有称为 current_state 的实际列，但记录的状态由状态机管理（不确定它存储状态的确切位置）。

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1 回答 1

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I was researching state machines also and, though I haven't implemented it yet in my project, I found this that might be helpful.

  1. Make sure your gemfile includes 

    gem "transitions", :require => ["transitions", "active_record/transitions"]

  2. Make sure your model has

    include ActiveRecord::Transitions

    rather than just 

    include Transitions

    and that it has a column called 'state' as this is where state is persisted.


The problem seemed to have been documented here:

http://dev.netizer.pl/transitions-state-machine-for-rails-3.html/comment-page-1#comment-41

And the documentation on github also outlines the setup for Rails

http://github.com/qoobaa/transitions

Using with Rails

This goes into your Gemfile:

gem "transitions", :require => ["transitions", "active_record/transitions"]

… and this into your AR model:

include ActiveRecord::Transitions

A note about persistence

The property used to persist the models’ state is named state (really!), which should be a string column wide enough to fit your longest state name. It should also be mentioned that #save! is called after every successful event.

Hope this is helpful, good luck!

于 2011-08-18T08:33:08.487 回答