Statum
Finite state machine for your objects
Supported Ruby 2.2.0+
- Installation
- Usage
- Basic usage
- Multiple state machines
- Hooks
- Contributing
- License
Installation
Add this line to your application's Gemfile:
gem 'statum'
And then execute:
$ bundle
Or install it yourself as:
$ gem install statum
Usage
Basic usage
Statum provides a DSL for defining state machine for your class
class Car
include Statum
attr_accessor :state
statum :state, initial: :idle do
state :idle
state :riding
event :ride, idle: :riding
end
end
Then Car
object will receive following methods:
car = Car.new
car.idle? # => true
car.riding? # => false
car.ride! # changes idle state to riding
You can define an array of states which will be able to fire event:
class Car
include Statum
attr_accessor :state
statum :state, initial: :idle do
state :idle
state :parked
state :riding
event :ride, %i[idle parked] => :riding
end
end
Also you can use any_state
helper to say, that event can be fired from any of defined states
class Car
include Statum
attr_accessor :state
statum :state, initial: :idle do
state :idle
state :parked
state :riding
event :ride, any_state => :riding
end
end
Multiple state machines
You can define more than one state machine on your object.
IMPORTANT use unique fields to work with two or more states
class Car
include Statum
attr_accessor :state, :engine
statum :state do
state :riding
state :idle
event :ride, idle: :riding
end
statum :engine do
state :stopped
state :started
event :start, stopped: :started
end
end
car = Car.new
car.start! # changes engine to started
car.ride! # changes state to riding
Hooks
You can be able to execute some procs before and after event will be fired
class Car
include Statum
attr_accessor :state, :started
statum :state, initial: :idle do
state :idle
state :riding
event :ride, idle: :riding,
before: -> { self.started = true },
after: :stop_engine
end
def stop_engine
self.started = false
end
end
And then before state changes will be executed before
proc, and after
changing - after
proc (in instance context).
If you will wait for argument in hook - the instance will be passed.
...
event :ride, idle: :riding,
before: -> (instance) { instance.started = true}
...
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/nulldef/statum.
License
The gem is available as open source under the terms of the MIT License.