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# Usage: | |
# | |
# class Mail | |
# include SimpleStateMachine | |
# | |
# self.initial_state = 'unread' | |
# self.transitions_map = { | |
# read: {from: 'unread', to: 'read'}, | |
# unread: {from: 'any', to: 'unread'}, | |
# delete: {from: 'any', to: 'deleted'}, | |
# spam: {from: 'any', to: 'spam'} | |
# } | |
# | |
# attr_accessor :state | |
# end | |
# | |
# mail = Mail.new | |
# mail.state # => 'unread' | |
# mail.read # => true | |
# mail.state # => 'read' | |
# mail.read_allowed? # => false | |
# mail.read! # => RuntimeError: Invalid transition from `read` by `read` | |
# | |
module SimpleStateMachine | |
def state | |
fail NotImplementedError | |
end | |
def state=(value) | |
fail NotImplementedError | |
end | |
def initialize(*) | |
super | |
self.state = self.class.initial_state if self.class.initial_state | |
end | |
def self.included(klass) | |
klass.extend ClassMethods | |
end | |
module ClassMethods | |
attr_accessor :initial_state | |
def transitions_map=(transitions_map) | |
transitions_map.each do |transition_name, options| | |
from = Array(options.fetch(:from)) | |
to = options.fetch(:to) | |
define_method("#{transition_name}_allowed?") do | |
!([state, 'any'] & from).empty? | |
end | |
define_method(transition_name) do | |
return unless send("#{transition_name}_allowed?") | |
self.state = to | |
true | |
end | |
define_method("#{transition_name}!") do | |
return true if send(transition_name) | |
raise "Invalid transition from `#{state}` by `#{transition_name}`" | |
end | |
end | |
end | |
end | |
end |
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