Module: DataMapper::Is::StateMachine::EventDsl

Defined in:
lib/dm-is-state_machine/is/dsl/event_dsl.rb

Overview

Event DSL (Domain Specific Language)

Instance Method Summary collapse

Instance Method Details

#event(name, &block) ⇒ Object

Define an event. This takes a block which describes all valid transitions for this event.

Example:

class TrafficLight
  include DataMapper::Resource
  property :id, Serial
  is :state_machine, :initial => :green, :column => :color do
    # state definitions go here...

    event :forward do
      transition :from => :green,  :to => :yellow
      transition :from => :yellow, :to => :red
      transition :from => :red,    :to => :green
    end
  end
end

transition takes a hash where :to is the state to transition to and :from is a state (or Array of states) from which this event can be fired.



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# File 'lib/dm-is-state_machine/is/dsl/event_dsl.rb', line 29

def event(name, &block)
  unless state_machine_context?(:is)
    raise InvalidContext, "Valid only in 'is :state_machine' block"
  end

  # ===== Setup context =====
  machine = @is_state_machine[:machine]
  event = Data::Event.new(name, machine)
  machine.events << event
  @is_state_machine[:event] = {
    :name   => name,
    :object => event
  }
  push_state_machine_context(:event)

  # ===== Define methods =====
  define_method("#{name}!") do
    transition!(name)
  end

  # Possible alternative to the above:
  # (class_eval is typically faster than define_method)
  #
  # self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
  #   def #{name}!
  #     machine.current_state_name = __send__(:"#{column}")
  #     machine.fire_event(name, self)
  #     __send__(:"#{column}="), machine.current_state_name
  #   end
  # RUBY

  yield if block_given?

  # ===== Teardown context =====
  pop_state_machine_context
end

#transition(options) ⇒ Object 



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# File 'lib/dm-is-state_machine/is/dsl/event_dsl.rb', line 66

def transition(options)
  unless state_machine_context?(:event)
    raise InvalidContext, "Valid only in 'event' block"
  end
  event_name   = @is_state_machine[:event][:name]
  event_object = @is_state_machine[:event][:object]

  from = options[:from]
  to   = options[:to]
  event_object.add_transition(from, to)
end