Question

I have a model that relies on state_machine to manage its different states. One particular event requires a before_transition as it needs to build a join table fore doing the transition. Unfortunately it doesn’t work.

class DocumentSet < ActiveRecord::Base

  state_machine :state, :initial => :draft do
    # Callbacks
    before_transition :on=>:submit, :do=>:populate_join_table

    # States
    state :draft
    state :submitted

    # Events
    event :submit do transition :draft=>:submitted, :if=>:can_submit? end
  end

def populate_join_table
   puts '::::::::: INSIDE POPULATE_JOIN_TABLE'
end

def can_submit?    
  raise "Document Set has no Document(s)" if self.document_versions.blank?
  true
end

Now when I do DocumentSet.submit, it actually never goes into the populate_join_table as it evaluates the can_submit? as false.

What am I missing?

Answer 1

Think I found the solution. Basically what happens is that state_machine first evaluates the :if condition, and only then does the before_transition.

So the order is:

If (GuardCondition == true)
  run before_transition
  run transition
  run before_transition