[Future request] :transitionsif option

[akalyaev]

Hello,

Usually, all my `ActiveRecord` models have a state_machine to control the state of the record (e.g. :new, :archived, :deleted). That is how I am implementing a safe delete mechanizm. All of the transitions of such a state_machine should only occur if object is persisted in the DB. Therefore, for each transition I have to duplicate `:if` condition.

    state_machine :state, :initial => :active do

      state :active

      state :archived

      state :deleted

      event :activate do

        transition any - :active => :active, :if => :persisted?

      end

      event :archive do

        transition :active => :archived, :if => :persisted?

      end

      event :del do

        transition any - :deleted => :deleted, :if => :persisted?

      end

    end

I thought, it would be nice to have an option like :transitionsif, which will be a method, proc or string to call to determine if any determined transition is possible.

   state_machine :state, :initial => :active, :transitionsif => :persisted? do

      state :active

      state :archived

      state :deleted

      event :activate do

        transition any - :active => :active

      end

      event :archive do

        transition :active => :archived

      end

      event :del do

        transition any - :deleted => :deleted

      end

    end

    

What do you think?