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# AASM - Ruby state machines
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[![Gem Version](https://badge.fury.io/rb/aasm.svg)](http://badge.fury.io/rb/aasm)
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[![Build Status](https://travis-ci.org/aasm/aasm.svg?branch=master)](https://travis-ci.org/aasm/aasm)
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[![Dependency Status](https://gemnasium.com/aasm/aasm.svg)](https://gemnasium.com/aasm/aasm)
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[![Code Climate](https://codeclimate.com/github/aasm/aasm/badges/gpa.svg)](https://codeclimate.com/github/aasm/aasm)
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This package contains AASM, a library for adding finite state machines to Ruby classes.
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AASM started as the *acts_as_state_machine* plugin but has evolved into a more generic library
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that no longer targets only ActiveRecord models. It currently provides adapters for
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[ActiveRecord](http://api.rubyonrails.org/classes/ActiveRecord/Base.html),
[Mongoid](http://mongoid.org/), and [Mongomapper](http://mongomapper.com/) but it can be used for any Ruby class, no matter what
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parent class it has (if any).
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## Upgrade from version 3 to 4
Take a look at the [README_FROM_VERSION_3_TO_4](https://github.com/aasm/aasm/blob/master/README_FROM_VERSION_3_TO_4.md) for details how to switch from version 3.x to 4.0 of _AASM_.
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## Usage
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Adding a state machine is as simple as including the AASM module and start defining
**states** and **events** together with their **transitions**:
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```ruby
class Job
include AASM
aasm do
state :sleeping, :initial => true
state :running
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state :cleaning
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event :run do
transitions :from => :sleeping, :to => :running
end
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event :clean do
transitions :from => :running, :to => :cleaning
end
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event :sleep do
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transitions :from => [:running, :cleaning], :to => :sleeping
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end
end
end
```
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This provides you with a couple of public methods for instances of the class `Job`:
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```ruby
job = Job.new
job.sleeping? # => true
job.may_run? # => true
job.run
job.running? # => true
job.sleeping? # => false
job.may_run? # => false
job.run # => raises AASM::InvalidTransition
```
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If you don't like exceptions and prefer a simple `true` or `false` as response, tell
AASM not to be *whiny*:
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```ruby
class Job
...
aasm :whiny_transitions => false do
...
end
end
job.running? # => true
job.may_run? # => false
job.run # => false
```
When firing an event, you can pass a block to the method, it will be called only if
the transition succeeds :
```ruby
job.run do
job.user.notify_job_ran # Will be called if job.may_run? is true
end
```
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### Callbacks
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You can define a number of callbacks for your transitions. These methods will be
called, when certain criteria are met, like entering a particular state:
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```ruby
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class Job
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include AASM
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aasm do
state :sleeping, :initial => true, :before_enter => :do_something
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state :running
after_all_transitions :log_status_change
event :run, :after => :notify_somebody do
before do
log('Preparing to run')
end
transitions :from => :sleeping, :to => :running, :after => Proc.new {|*args| set_process(*args) }
transitions :from => :running, :to => :finished, :after => LogRunTime
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end
event :sleep do
after do
...
end
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error do |e|
...
end
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transitions :from => :running, :to => :sleeping
end
end
def log_status_change
puts "changing from #{aasm.from_state} to #{aasm.to_state} (event: #{aasm.current_event})"
end
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def set_process(name)
...
end
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def do_something
...
end
def notify_somebody(user)
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...
end
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end
class LogRunTime
def call
log "Job was running for X seconds"
end
end
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```
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In this case `do_something` is called before actually entering the state `sleeping`,
while `notify_somebody` is called after the transition `run` (from `sleeping` to `running`)
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is finished.
AASM will also initialize `LogRunTime` and run the `call` method for you after the transition from `runnung` to `finished` in the example above. You can pass arguments to the class by defining an initialize method on it, like this:
```
class LogRunTime
# optional args parameter can be omitted, but if you define initialize
# you must accept the model instance as the first parameter to it.
def initialize(job, args = {})
@job = job
end
def call
log "Job was running for #{@job.run_time} seconds"
end
end
```
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Here you can see a list of all possible callbacks, together with their order of calling:
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```ruby
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begin
event before_all_events
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event before
event guards
transition guards
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old_state before_exit
old_state exit
after_all_transitions
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transition after
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new_state before_enter
new_state enter
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...update state...
event success # if persist successful
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old_state after_exit
new_state after_enter
event after
event after_all_events
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rescue
event error
event error_on_all_events
ensure
event ensure
event ensure_on_all_events
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end
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```
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Also, you can pass parameters to events:
```ruby
job = Job.new
job.run(:running, :defragmentation)
```
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In this case the `set_process` would be called with `:defragmentation` argument.
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Note that when passing arguments to a state transition, the first argument must be the desired end state. In the above example, we wish to transition to `:running` state and run the callback with `:defragmentation` argument. You can also pass in `nil` as the desired end state, and AASM will try to transition to the first end state defined for that event.
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In case of an error during the event processing the error is rescued and passed to `:error`
callback, which can handle it or re-raise it for further propagation.
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During the transition's `:after` callback (and reliably only then, or in the global
`after_all_transitions` callback) you can access the originating state (the from-state)
and the target state (the to state), like this:
```ruby
def set_process(name)
logger.info "from #{aasm.from_state} to #{aasm.to_state}"
end
```
#### The current event triggered
While running the callbacks you can easily retrieve the name of the event triggered
by using `aasm.current_event`:
```ruby
# taken the example callback from above
def do_something
puts "triggered #{aasm.current_event}"
end
```
and then
```ruby
job = Job.new
# without bang
job.sleep # => triggered :sleep
# with bang
job.sleep! # => triggered :sleep!
```
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### Guards
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Let's assume you want to allow particular transitions only if a defined condition is
given. For this you can set up a guard per transition, which will run before actually
running the transition. If the guard returns `false` the transition will be
denied (raising `AASM::InvalidTransition` or returning `false` itself):
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```ruby
class Cleaner
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include AASM
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aasm do
state :idle, :initial => true
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state :cleaning
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event :clean do
transitions :from => :idle, :to => :cleaning, :guard => :cleaning_needed?
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end
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event :clean_if_needed do
transitions :from => :idle, :to => :cleaning do
guard do
cleaning_needed?
end
end
transitions :from => :idle, :to => :idle
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end
end
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def cleaning_needed?
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false
end
end
job = Cleaner.new
job.may_clean? # => false
job.clean # => raises AASM::InvalidTransition
job.may_clean_if_needed? # => true
job.clean_if_needed! # idle
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```
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You can even provide a number of guards, which all have to succeed to proceed
```ruby
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def walked_the_dog?; ...; end
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event :sleep do
transitions :from => :running, :to => :sleeping, :guards => [:cleaning_needed?, :walked_the_dog?]
end
```
If you want to provide guards for all transitions within an event, you can use event guards
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```ruby
event :sleep, :guards => [:walked_the_dog?] do
transitions :from => :running, :to => :sleeping, :guards => [:cleaning_needed?]
transitions :from => :cleaning, :to => :sleeping
end
```
If you prefer a more Ruby-like guard syntax, you can use `if` and `unless` as well:
```ruby
event :clean do
transitions :from => :running, :to => :cleaning, :if => :cleaning_needed?
end
event :sleep do
transitions :from => :running, :to => :sleeping, :unless => :cleaning_needed?
end
end
```
### Transitions
In the event of having multiple transitions for an event, the first transition that successfully completes will stop other transitions in the same event from being processed.
```ruby
require 'aasm'
class Job
include AASM
aasm do
state :stage1, :initial => true
state :stage2
state :stage3
state :completed
event :stage1_completed do
transitions from: :stage1, to: :stage3, guard: :stage2_completed?
transitions from: :stage1, to: :stage2
end
end
def stage2_completed?
true
end
end
job = Job.new
job.stage1_completed
job.aasm.current_state # stage3
```
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### Multiple state machines per class
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Multiple state machines per class are supported. Be aware though that _AASM_ has been
built with one state machine per class in mind. Nonetheless, here's how to do it:
```ruby
class SimpleMultipleExample
include AASM
aasm(:move) do
state :standing, :initial => true
state :walking
state :running
event :walk do
transitions :from => :standing, :to => :walking
end
event :run do
transitions :from => [:standing, :walking], :to => :running
end
event :hold do
transitions :from => [:walking, :running], :to => :standing
end
end
aasm(:work) do
state :sleeping, :initial => true
state :processing
event :start do
transitions :from => :sleeping, :to => :processing
end
event :stop do
transitions :from => :processing, :to => :sleeping
end
end
end
simple = SimpleMultipleExample.new
simple.aasm(:move).current_state
# => :standing
simple.aasm(:work).current
# => :sleeping
simple.start
simple.aasm(:move).current_state
# => :standing
simple.aasm(:work).current
# => :processing
```
_AASM_ doesn't prohibit to define the same event in more than one state machine. The
latest definition "wins" and overrides previous definitions. Nonetheless, a warning is issued:
`SimpleMultipleExample: The aasm event name run is already used!`.
All _AASM_ class- and instance-level `aasm` methods accept a state machine selector.
So, for example, to use inspection on a class level, you have to use
```ruby
SimpleMultipleExample.aasm(:work).states
# => [:standing, :walking, :running]
```
*Final note*: Support for multiple state machines per class is a pretty new feature
(since version `4.3`), so please bear with us in case it doesn't work as expected.
### Extending AASM
AASM allows you to easily extend `AASM::Base` for your own application purposes.
Let's suppose we have common logic across many AASM models. We can embody this logic in a sub-class of `AASM::Base`.
```ruby
class CustomAASMBase < AASM::Base
# A custom transiton that we want available across many AASM models.
def count_transitions!
klass.class_eval do
aasm :with_klass => CustomAASMBase do
after_all_transitions :increment_transition_count
end
end
end
# A custom annotation that we want available across many AASM models.
def requires_guards!
klass.class_eval do
attr_reader :authorizable_called,
:transition_count,
:fillable_called
def authorizable?
@authorizable_called = true
end
def fillable?
@fillable_called = true
end
def increment_transition_count
@transition_count ||= 0
@transition_count += 1
end
end
end
end
```
When we declare our model that has an AASM state machine, we simply declare the AASM block with a `:with` key to our own class.
```ruby
class SimpleCustomExample
include AASM
# Let's build an AASM state machine with our custom class.
aasm :with_klass => CustomAASMBase do
requires_guards!
count_transitions!
state :initialised, :initial => true
state :filled_out
state :authorised
event :fill_out do
transitions :from => :initialised, :to => :filled_out, :guard => :fillable?
end
event :authorise do
transitions :from => :filled_out, :to => :authorised, :guard => :authorizable?
end
end
end
```
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### ActiveRecord
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AASM comes with support for ActiveRecord and allows automatic persisting of the object's
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state in the database.
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```ruby
class Job < ActiveRecord::Base
include AASM
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aasm do # default column: aasm_state
state :sleeping, :initial => true
state :running
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event :run do
transitions :from => :sleeping, :to => :running
end
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event :sleep do
transitions :from => :running, :to => :sleeping
end
end
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end
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```
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You can tell AASM to auto-save the object or leave it unsaved
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```ruby
job = Job.new
job.run # not saved
job.run! # saved
```
Saving includes running all validations on the `Job` class, and returns `true` if
successful or `false` if errors occur. Exceptions are not raised.
If you want make sure the state gets saved without running validations (and
thereby maybe persisting aninvalid object state), simply tell AASM to skip the
validations. Be aware that when skipping validations, only the state column will
be updated in the database (just like ActiveRecord `change_column` is working).
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```ruby
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class Job < ActiveRecord::Base
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include AASM
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aasm :skip_validation_on_save => true do
state :sleeping, :initial => true
state :running
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event :run do
transitions :from => :sleeping, :to => :running
end
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event :sleep do
transitions :from => :running, :to => :sleeping
end
end
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end
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```
If you want to make sure that the _AASM_ column for storing the state is not directly assigned,
configure _AASM_ to not allow direct assignment, like this:
```ruby
class Job < ActiveRecord::Base
include AASM
aasm :no_direct_assignment => true do
state :sleeping, :initial => true
state :running
event :run do
transitions :from => :sleeping, :to => :running
end
end
end
```
resulting in this:
```ruby
job = Job.create
job.aasm_state # => 'sleeping'
job.aasm_state = :running # => raises AASM::NoDirectAssignmentError
job.aasm_state # => 'sleeping'
```
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#### ActiveRecord enums
You can use
[enumerations](http://edgeapi.rubyonrails.org/classes/ActiveRecord/Enum.html)
in Rails 4.1+ for your state column:
```ruby
class Job < ActiveRecord::Base
include AASM
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enum state: {
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sleeping: 5,
running: 99
}
aasm :column => :state, :enum => true do
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state :sleeping, :initial => true
state :running
end
end
```
You can explicitly pass the name of the method which provides access
to the enumeration mapping as a value of ```enum```, or you can simply
set it to ```true```. In the latter case AASM will try to use
pluralized column name to access possible enum states.
Furthermore, if your column has integer type (which is normally the
case when you're working with Rails enums), you can omit ```:enum```
setting --- AASM auto-detects this situation and enabled enum
support. If anything goes wrong, you can disable enum functionality
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and fall back to the default behavior by setting ```:enum```
to ```false```.
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### Sequel
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AASM also supports [Sequel](http://sequel.jeremyevans.net/) besides _ActiveRecord_, _Mongoid_, and _MongoMapper_.
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```ruby
class Job < Sequel::Model
include AASM
aasm do # default column: aasm_state
...
end
end
```
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However it's not yet as feature complete as _ActiveRecord_. For example, there are
scopes defined yet. See [Automatic Scopes](#automatic-scopes).
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### Dynamoid
Since version `4.8.0` _AASM_ also supports [Dynamoid](http://joshsymonds.com/Dynamoid/) as
persistence ORM.
### Mongoid
AASM also supports persistence to Mongodb if you're using Mongoid. Make sure
to include Mongoid::Document before you include AASM.
```ruby
class Job
include Mongoid::Document
include AASM
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field :aasm_state
aasm do
...
end
end
```
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### MongoMapper
AASM also supports persistence to Mongodb if you're using MongoMapper. Make sure
to include MongoMapper::Document before you include AASM.
```ruby
class Job
include MongoMapper::Document
include AASM
key :aasm_state, Symbol
aasm do
...
end
end
```
### Automatic Scopes
AASM will automatically create scope methods for each state in the model.
```ruby
class Job < ActiveRecord::Base
include AASM
aasm do
state :sleeping, :initial => true
state :running
state :cleaning
end
def self.sleeping
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"This method name is already in use"
end
end
```
```ruby
class JobsController < ApplicationController
def index
@running_jobs = Job.running
@recent_cleaning_jobs = Job.cleaning.where('created_at >= ?', 3.days.ago)
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# @sleeping_jobs = Job.sleeping #=> "This method name is already in use"
end
end
```
If you don't need scopes (or simply don't want them), disable their creation when
defining the `AASM` states, like this:
```ruby
class Job < ActiveRecord::Base
include AASM
aasm :create_scopes => false do
state :sleeping, :initial => true
state :running
state :cleaning
end
end
```
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### Transaction support
Since version *3.0.13* AASM supports ActiveRecord transactions. So whenever a transition
callback or the state update fails, all changes to any database record are rolled back.
Mongodb does not support transactions.
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There are currently 3 transactional callbacks that can be handled on the event, and 2 transactional callbacks for all events.
```ruby
event before_all_transactions
event before_transaction
event aasm_fire_event (within transaction)
event after_commit (if event successful)
event after_transaction
event after_all_transactions
```
If you want to make sure a depending action happens only after the transaction is committed,
use the `after_commit` callback along with the auto-save (bang) methods, like this:
```ruby
class Job < ActiveRecord::Base
include AASM
aasm do
state :sleeping, :initial => true
state :running
event :run, :after_commit => :notify_about_running_job do
transitions :from => :sleeping, :to => :running
end
end
def notify_about_running_job
...
end
end
job = Job.where(state: 'sleeping').first!
job.run! # Saves the model and triggers the after_commit callback
```
Note that the following will not run the `after_commit` callbacks because
the auto-save method is not used:
```ruby
job = Job.where(state: 'sleeping').first!
job.run
job.save! #notify_about_running_job is not run
```
If you want to encapsulate state changes within an own transaction, the behavior
of this nested transaction might be confusing. Take a look at
[ActiveRecord Nested Transactions](http://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html)
if you want to know more about this. Nevertheless, AASM by default requires a new transaction
`transaction(:requires_new => true)`. You can override this behavior by changing
the configuration
```ruby
class Job < ActiveRecord::Base
include AASM
aasm :requires_new_transaction => false do
...
end
...
end
```
which then leads to `transaction(:requires_new => false)`, the Rails default.
### Pessimistic Locking
AASM supports [Active Record pessimistic locking via `with_lock`](http://api.rubyonrails.org/classes/ActiveRecord/Locking/Pessimistic.html#method-i-with_lock) for database persistence layers.
| Option | Purpose |
| ------ | ------- |
| `false` (default) | No lock is obtained | |
| `true` | Obtain a blocking pessimistic lock e.g. `FOR UPDATE` |
| String | Obtain a lock based on the SQL string e.g. `FOR UPDATE NOWAIT` |
```ruby
class Job < ActiveRecord::Base
include AASM
aasm :requires_lock => true do
...
end
...
end
```
```ruby
class Job < ActiveRecord::Base
include AASM
aasm :requires_lock => 'FOR UPDATE NOWAIT' do
...
end
...
end
```
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### Column name & migration
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As a default AASM uses the column `aasm_state` to store the states. You can override
this by defining your favorite column name, using `:column` like this:
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```ruby
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class Job < ActiveRecord::Base
include AASM
aasm :column => 'my_state' do
...
end
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end
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```
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Whatever column name is used, make sure to add a migration to provide this column
(of type `string`):
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```ruby
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class AddJobState < ActiveRecord::Migration
def self.up
add_column :jobs, :aasm_state, :string
end
def self.down
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remove_column :jobs, :aasm_state
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end
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end
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```
### Inspection
AASM supports a couple of methods to find out which states or events are provided or permitted.
Given this `Job` class:
```ruby
# show all states
Job.aasm.states.map(&:name)
=> [:sleeping, :running, :cleaning]
job = Job.new
# show all permitted (reachable / possible) states
job.aasm.states(:permitted => true).map(&:name)
=> [:running]
job.run
job.aasm.states(:permitted => true).map(&:name)
=> [:cleaning, :sleeping]
# show all possible (triggerable) events (allowed by transitions)
job.aasm.events.map(&:name)
=> [:sleep]
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job.aasm.events(:reject => :sleep).map(&:name)
=> []
# list states for select
Job.aasm.states_for_select
=> [["Sleeping", "sleeping"], ["Running", "running"], ["Cleaning", "cleaning"]]
```
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### RubyMotion support
To use AASM with a RubyMotion project, use it with the [motion-bundler](https://github.com/archan937/motion-bundler) gem.
Warnings:
- Due to the way key-value observation (KVO) works in iOS,
you currently CANNOT use AASM with an object you are observing. (Yes.. that's pretty sad).
- Due to RubyMotion Proc's lack of 'source_location' method, it may be harder
to find out the origin of a "cannot transition from" error. I would recommend using
the 'instance method symbol / string' way whenever possible when defining guardians and callbacks.
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### Testing
AASM provides some matchers for [RSpec](http://rspec.info): `transition_from`, `have_state`, `allow_event` and `allow_transition_to`. Add `require 'aasm/rspec'` to your `spec_helper.rb` file and use them like this
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```ruby
# classes with only the default state machine
job = Job.new
expect(job).to transition_from(:sleeping).to(:running).on_event(:run)
expect(job).not_to transition_from(:sleeping).to(:cleaning).on_event(:run)
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expect(job).to have_state(:sleeping)
expect(job).not_to have_state(:running)
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expect(job).to allow_event :run
expect(job).to_not allow_event :clean
expect(job).to allow_transition_to(:running)
expect(job).to_not allow_transition_to(:cleaning)
# on_event also accept arguments
expect(job).to transition_from(:sleeping).to(:running).on_event(:run, :defragmentation)
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# classes with multiple state machine
multiple = SimpleMultipleExample.new
expect(multiple).to transition_from(:standing).to(:walking).on_event(:walk).on(:move)
expect(multiple).to_not transition_from(:standing).to(:running).on_event(:walk).on(:move)
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expect(multiple).to have_state(:standing).on(:move)
expect(multiple).not_to have_state(:walking).on(:move)
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expect(multiple).to allow_event(:walk).on(:move)
expect(multiple).to_not allow_event(:hold).on(:move)
expect(multiple).to allow_transition_to(:walking).on(:move)
expect(multiple).to_not allow_transition_to(:running).on(:move)
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expect(multiple).to transition_from(:sleeping).to(:processing).on_event(:start).on(:work)
expect(multiple).to_not transition_from(:sleeping).to(:sleeping).on_event(:start).on(:work)
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expect(multiple).to have_state(:sleeping).on(:work)
expect(multiple).not_to have_state(:processing).on(:work)
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expect(multiple).to allow_event(:start).on(:move)
expect(multiple).to_not allow_event(:stop).on(:move)
expect(multiple).to allow_transition_to(:processing).on(:move)
expect(multiple).to_not allow_transition_to(:sleeping).on(:move)
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```
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## <a id="installation">Installation ##
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### Manually from RubyGems.org ###
```sh
% gem install aasm
```
### Or if you are using Bundler ###
```ruby
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# Gemfile
gem 'aasm'
```
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### Building your own gems ###
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```sh
% rake build
% sudo gem install pkg/aasm-x.y.z.gem
```
### Generators
After installing Aasm you can run generator:
```sh
% rails generate aasm NAME [COLUMN_NAME]
```
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Replace NAME with the Model name, COLUMN_NAME is optional(default is 'aasm_state').
This will create a model (if one does not exist) and configure it with aasm block.
For Active record orm a migration file is added to add aasm state column to table.
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## Latest changes ##
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Take a look at the [CHANGELOG](https://github.com/aasm/aasm/blob/master/CHANGELOG.md) for details about recent changes to the current version.
## Questions? ##
Feel free to
* [create an issue on GitHub](https://github.com/aasm/aasm/issues)
* [ask a question on StackOverflow](http://stackoverflow.com) (tag with `aasm`)
* send us a tweet [@aasm](http://twitter.com/aasm)
## Maintainers ##
* [Scott Barron](https://github.com/rubyist) (20062009, original author)
* [Travis Tilley](https://github.com/ttilley) (20092011)
* [Thorsten Böttger](http://github.com/alto) (since 2011)
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## Contributing ##
1. Read the [Contributor Code of Conduct](https://github.com/aasm/aasm/blob/master/CODE_OF_CONDUCT.md)
2. Fork it
3. Create your feature branch (git checkout -b my-new-feature)
4. Commit your changes (git commit -am 'Added some feature')
5. Push to the branch (git push origin my-new-feature)
6. Create new Pull Request
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## Warranty ##
This software is provided "as is" and without any express or
implied warranties, including, without limitation, the implied
warranties of merchantibility and fitness for a particular
purpose.
## License ##
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Copyright (c) 2006-2016 Scott Barron
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.