State Machines

state_machine_callbacks_with_params.rb

# To get parameters from your controller inside your transition callback

# transition : cannot be changed to a different variable name. It should always be transition
# my_model   : will always have the current object of the model class in which your state machine is defined
#              can add any variable name   
# params     : Actual parameters are stored in transition.args which is an array of parameters passed

class MyModel
  
  def update_my_model
    @object.select(params) # calls the select event from state machine
  end
  
  state_machine :initial => :started do
    before_transition to: :selected do |my_model,transition|
      params = transition.args.first
      # do something with params
      # do something with my_model object
      my_model.column = params[:column]
      
      # return false if you do not want the transition to complete based on condition
      return false unless my_model.save
    end
  
    event :select do
      transition :started => :selected
    end
  end
  
end