Question

I am developing application in rails , where i have made use of state_machine (https://github.com/pluginaweek/state_machine/).

Here i wanted to check condition in one state , based on condition
state changes from another state . (i.e consider state1 , state2 and
state3 are states if(a>b) {state1 => state2 }else {state1 =>state3}) ,

i wanted to know how this will be accomplished in state machine .
kindly help me out in this

Answer 1

In state_machine, you define events that change the state of the underlying object. You can also set the state attribute to the state that you want.

In your case you’d do:

a.state = a > b ? "state2" : "state3"
a.save!

You can also check the state with:

a.state1?

What you should do is define an event that describes the transition from state1 to state2 or state3. For instance:

state_machines :state, initial: :state1 do
  ... 

  event :go_to_state2 do
    transition state1: :state2
  end

  event :go_to_state3 do
    transition state1: :state3
  end

  ...
end

Then, you transition state like this:

if a > b
  a.go_to_state2!
else
  a.go_to_state3!
end

Using the events are a lot cleaner way of manipulating the state. This is all covered in the Readme on the plugin’s github page