state_machine only works for new records

Question

I can't seem to get the state_machine gem (http://github.com/pluginaweek/state_machine/) to work on existing records (it works correctly on new records).

Here's my model:

class Comment < ActiveRecord::Base
  state_machine :state, :initial => :pending do
    event :publish do
      transition all => :published
    end
  end
end

and here's an IRB session that demonstrates the issue (I did ActiveRecord::Base.logger = Logger.new(STDOUT) to make it easier to read):

>> c = Comment.new
=> #<Comment id: nil, song_id: nil, author: nil, body: nil, created_at: nil, updated_at: nil, state: "pending">
>> c.state
=> "pending"
>> c.publish
  Comment Create (0.6ms)   INSERT INTO "comments" ("updated_at", "body", "author", "song_id", "created_at", "state") VALUES('2009-11-02 02:44:37', NULL, NULL, NULL, '2009-11-02 02:44:37', 'published')
=> true
>> Comment.last.state
  Comment Load (0.4ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> "published"
>> c = Comment.create
  Comment Create (0.5ms)   INSERT INTO "comments" ("updated_at", "body", "author", "song_id", "created_at", "state") VALUES('2009-11-02 02:44:47', NULL, NULL, NULL, '2009-11-02 02:44:47', 'pending')
=> #<Comment id: 4, song_id: nil, author: nil, body: nil, created_at: "2009-11-02 02:44:47", updated_at: "2009-11-02 02:44:47", state: "pending">
>> c.publish
=> true
>> c.save
=> true
>> Comment.last.state
  Comment Load (0.4ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> "pending"

I.e., everything works fine when I publish an unsaved comment, but when I try to publish a comment that's already saved, nothing happens.

Another Edit: Perhaps the root of the problem?

=> true
>> a = Comment.last
  Comment Load (1.3ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> #<Comment id: 3, song_id: nil, author: nil, body: nil, created_at: "2009-11-03 03:03:54", updated_at: "2009-11-03 03:03:54", state: "pending">
>> a.state
=> "pending"
>> a.publish
=> true
>> a.state
=> "published"
>> a.state_changed?
=> false

I.e., even though the state has actually changed, state_changed? is returning false and therefore Rails won't update the corresponding database row when I call save.

It works when I turn off partial updates, but not when I try state_will_change!:

>> Comment.partial_updates = false
=> false
>> c = Comment.create
  Comment Create (0.5ms)   INSERT INTO "comments" ("updated_at", "body", "author", "song_id", "created_at", "state") VALUES('2009-11-07 05:06:49', NULL, NULL, NULL, '2009-11-07 05:06:49', 'pending')
=> #<Comment id: 7, song_id: nil, author: nil, body: nil, created_at: "2009-11-07 05:06:49", updated_at: "2009-11-07 05:06:49", state: "pending">
>> c.publish
  Comment Update (0.9ms)   UPDATE "comments" SET "created_at" = '2009-11-07 05:06:49', "author" = NULL, "state" = 'published', "body" = NULL, "song_id" = NULL, "updated_at" = '2009-11-07 05:06:53' WHERE "id" = 7
=> true
>> Comment.last.state
  Comment Load (0.5ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> "published"
>> Comment.partial_updates = true
=> true
>> c = Comment.create
  Comment Create (0.8ms)   INSERT INTO "comments" ("updated_at", "body", "author", "song_id", "created_at", "state") VALUES('2009-11-07 05:07:21', NULL, NULL, NULL, '2009-11-07 05:07:21', 'pending')
=> #<Comment id: 8, song_id: nil, author: nil, body: nil, created_at: "2009-11-07 05:07:21", updated_at: "2009-11-07 05:07:21", state: "pending">
>> c.state_will_change!
=> "pending"
>> c.publish
=> true
>> c.save
=> true
>> Comment.last.state
  Comment Load (0.5ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> "pending"

EDIT:

More weirdness:

>> a = Comment.last
  Comment Load (1.2ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> #<Comment id: 5, song_id: nil, author: nil, body: nil, created_at: "2009-11-02 06:33:19", updated_at: "2009-11-02 06:33:19", state: "pending">
>> a.state
=> "pending"
>> a.publish
=> true
>> a.state
=> "published"
>> a.save
=> true
>> a.id
=> 5
>> Comment.find(5).state
  Comment Load (0.3ms)   SELECT * FROM "comments" WHERE ("comments"."id" = 5) 
=> "pending"

Compare to:

>> a = Comment.last
  Comment Load (0.3ms)   SELECT * FROM "comments" ORDER BY comments.id DESC LIMIT 1
=> #<Comment id: 5, song_id: nil, author: nil, body: nil, created_at: "2009-11-02 06:33:19", updated_at: "2009-11-02 06:33:19", state: "pending">
>> a.state = "published"
=> "published"
>> a.save
  Comment Update (0.6ms)   UPDATE "comments" SET "state" = 'published', "updated_at" = '2009-11-02 08:29:34' WHERE "id" = 5
=> true
>> a.id
=> 5
>> Comment.find(5).state
  Comment Load (0.4ms)   SELECT * FROM "comments" WHERE ("comments"."id" = 5) 
=> "published"

Answer 1

I came over the same issue 3 years after so it worth answering here to save other folks's time.

You need to have column called 'state' in your table, so state_machine will able to make the state persistant.

Just add it to your migration - t.string :state

Answer 2

Can you please retry your state transitions with publish**!** instead of publish