Storing transitions to memory

[jdliaw]

We wanted to use this state machine as only in memory for models whose state history we were not as concerned with. Without specifying a transition_class, transitions are stored to memory, but the current_state, transition_to methods etc. look into the state_machine.history to determine the current_state or whether a transition can be made. This history doesn't exist without the transition_class so the state machine was not reading from memory where the transitions were being stored.

As a fix, our state_machine method looked like this:

def state_machine
  @_state_machine ||= begin
     @state_machine = OrderStateMachine.new(self)
     if state
       @state_machine.history << Statesman::Adapters::MemoryTransition.new(state, 0)
     end
    @state_machine
  end
end

This was used in multiple places for us, so it could be useful for others as well, who want to save their transitions in memory.

[nicolas-besnard]

You can also put this directly on your state machine:

def after_initialize
  history << @transition_class.new(object.state || self.class.initial_state, 0)
end

Maybe we should try to work on a PR to add this to the documentation.

(all credits to @RobertAudi)