Module: Golem::ClassMethods

Defined in:
lib/golem.rb

Instance Method Summary collapse

Instance Method Details

#define_statemachine(statemachine_name = nil, options = {}, &block) ⇒ Object

Raises:



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# File 'lib/golem.rb', line 43

def define_statemachine(statemachine_name = nil, options = {}, &block)
  default_statemachine_name = :statemachine
  
  class_attribute :statemachines unless respond_to?(:statemachines)
  self.statemachines ||= {}
  
  if statemachines.has_key?(statemachine_name || default_statemachine_name)
    if statemachine_name == default_statemachine_name
      raise ArgumentError, "If you are declaring more than one statemachine within the same class, you must give each statemachine a unique name (i.e. define_statemachine(name) do ... end)."
    else
      raise ArgumentError, "Cannot declare a statemachine under #{(statemachine_name || default_statemachine_name).inspect} because this statemachine name is already taken."
    end
  end

  statemachine_def = Golem::DSL::StateMachineDef.new(self, statemachine_name, &block)
  
  statemachine = statemachine_def.machine

  raise Golem::DefinitionSyntaxError, "No initial_state defined for statemachine #{statemachine}!" if statemachine.initial_state.blank?

  self.statemachines[statemachine_name || default_statemachine_name] = statemachine
  class_eval do
    define_method(statemachine_name || default_statemachine_name) do
      statemachines[statemachine_name || default_statemachine_name]
    end
  end

  state_attribute = statemachine_def.state_attribute

  if state_attribute.blank?
    if statemachine_name.nil?
      state_attribute = :state
    else
      state_attribute = "#{statemachine_name}_state".to_sym
    end
  end

  statemachine.state_attribute = state_attribute

  # state reader
  define_method("#{state_attribute}".to_sym) do
    # TODO: the second two cases here should be collapsed into the first
    case
    when statemachine.state_attribute_reader
      if statemachine.state_attribute_reader.respond_to?(:call)
        state = statemachine.state_attribute_reader.call(self)
      else
        state = self.send(statemachine.state_attribute_reader)
      end
    when Object.const_defined?('ActiveRecord') && self.kind_of?(ActiveRecord::Base)
      state = self[state_attribute.to_s] && self[state_attribute.to_s].to_sym
    else
      state = self.instance_variable_get("@#{state_attribute}")
    end
    
    state ||= statemachine.initial_state
    state   = state.to_sym if state.is_a?(String)

    raise InvalidStateError, "#{self} is in an unrecognized state (#{state.inspect})" unless statemachine.states[state]

    state   = statemachine.states[state].name
    
    return state
  end

  # state writer
  define_method("#{state_attribute}=".to_sym) do |new_state|
    new_state = new_state.name if new_state.respond_to?(:name)
    new_state = new_state.to_sym
    raise ArgumentError, "#{new_state.inspect} is not a valid state for #{statemachine}!" unless statemachine.states[new_state]
    
    # transition takes care of calling on_exit, so don't do it if we're in the middle of a transition
    unless statemachine.is_transitioning?
      from_state_obj = statemachine.states[self.send("#{state_attribute}")]
      from_state_obj.callbacks[:on_exit].call(self) if from_state_obj.callbacks[:on_exit]
    end
    
    # TODO: the second two cases here whould be collapsed into the first
    case
    when statemachine.state_attribute_writer
      if statemachine.state_attribute_writer.respond_to?(:call)
        statemachine.state_attribute_writer.call(self, new_state)
      else
        self.send(statemachine.state_attribute_writer, new_state)
      end
    when Object.const_defined?('ActiveRecord') && self.kind_of?(ActiveRecord::Base)
      self[state_attribute.to_s] = new_state.to_s # store as String rather than Symbol to prevent serialization weirdness
    else
      self.instance_variable_set("@#{state_attribute}", new_state)
    end
    
    # transition takes care of calling on_entry, so don't do it if we're in the middle of a transition
    unless statemachine.is_transitioning?
      new_state_obj = statemachine.states[new_state]
      new_state_obj.callbacks[:on_enter].call(self) if new_state_obj.callbacks[:on_enter]
    end
  end

  validate :check_for_transition_errors if respond_to? :validate

  define_method(:transition_errors) do
    @transition_errors ||= []
  end

  define_method(:check_for_transition_errors) do
    if transition_errors && !transition_errors.empty?
      transition_errors.each do |err|
        errors.add_to_base(err)
      end
    end
  end


  statemachine.events.each do |event|
    self.class_eval do
      
      # For every event defined in each statemachine we define a regular
      # (non-exception-raising) method and bang! (exception-raising).
      # This allows for triggering the event by calling the appropriate
      # event-named method on the object.
      [event.name,"#{event.name}!"].each do |meth|
        define_method(meth) do |*args|
          fire_proc = lambda do
            impossible = {}
            results = self.statemachines.collect do |name, sm|
              begin
                if meth =~ /!$/
                  sm.fire_event_with_exceptions(self, event, *args)
                else
                  sm.fire_event_without_exceptions(self, event, *args)
                end
              rescue Golem::ImpossibleEvent => e
                impossible[sm] = e
              end
            end
            if impossible.size == self.statemachines.size
              # all statemachines raised Golem::ImpossibleEvent
              message = impossible.values.collect{|e| e.message}.uniq.join("\n")
              events = impossible.values.collect{|e| e.event}.uniq
              events = events[0] if events.size <= 1
              objects = impossible.values.collect{|e| e.object}.uniq
              objects = objects[0] if objects.size <= 1
              reasons = impossible.values.collect{|e| e.reasons}.flatten.uniq
              reasons = reasons[0] if reasons.size <= 1
              raise Golem::ImpossibleEvent.new(message, events, objects, reasons)
            end
            results.all?{|result| result == true}
          end

          if self.class.respond_to?(:transaction)
             # Wrap event call inside a transaction, if supported (i.e. for ActiveRecord)
            self.class.transaction(&fire_proc)
          else
            fire_proc.call
          end
        end
      end

      define_method("determine_#{"#{statemachine_name}_" if statemachine_name}state_after_#{event.name}") do |*args|
        transition = nil
        if self.class.respond_to?(:transaction)
          self.class.transaction do
            # TODO: maybe better to use fire_event + transaction rollback to simulate event firing?
            transition = statemachine.determine_transition_on_event(self, event, *args)
          end
        else
          transition = statemachine.determine_transition_on_event(self, event, *args)
        end

        transition ? transition.to.name : nil
      end
    end
  end
end