Dynamic State Machine in Ruby? Do State Machines Have to be Classes?
- by viatropos
Question is, are state machines always defined statically (on classes)? Or is there a way for me to have it so each instance of the class with has it's own set of states?
I'm checking out Stonepath for implementing a Task Engine. I don't really see the distinction between "states" and "tasks" in there, so I'm thinking I could just map a Task directly to a state. This would allow me to be able to define task-lists (or workflows) dynamically, without having to do things like:
aasm_event :evaluate do
transitions :to => :in_evaluation, :from => :pending
end
aasm_event :accept do
transitions :to => :accepted, :from => :pending
end
aasm_event :reject do
transitions :to => :rejected, :from => :pending
end
Instead, a WorkItem (the main workflow/task manager model), would just have many tasks. Then the tasks would work like states, so I could do something like this:
aasm_initial_state :initial
tasks.each do |task|
aasm_state task.name.to_sym
end
previous_state = nil
tasks.each do |tasks|
aasm_event task.name.to_sym do
transitions :to => "#{task.name}_phase".to_sym, :from => previous_state ? "#{task.name}_phase" : "initial"
end
previous_state = state
end
However, I can't do that with the aasm gem because those methods (aasm_state and aasm_event) are class methods, so every instance of the class with that state machine has the same states. I want it so a "WorkItem" or "TaskList" dynmically creates a sequence of states and transitions based on the tasks it has.
This would allow me to dynamically define workflows and just have states map to tasks.
Are state machines ever used like this?
