Codecabulary Home / Learn Ruby / State Machines
State machines represent a very big and complex topic in the world of computer science; navigating to the state machine gem's ReadMe file can make grown men cry. But state machines don't have to the be that complicated!
Take a simple example of moderating a comment for a blog post. The user is able to flag an inappropriate comment. That causes the comment to appear in a review section for the site admin. The site admin then decides whether he or she wishes to approve or remove the comment. Only approved comments are shown.
First, install the state machine gem:
Don't forget to add
state to your model (string).
Then edit your model to include states:
state_machine :initial => :approved do state :approved state :flagged state :removed event :flag do transition :approved => :flagged end event :approve do transition all => :approved end event :remove do transition :flagged => :removed end end
Using the all transition means that you can approve a comment no matter what state your record is.
Congratulations, you just created a state machine! Now you could perform actions such as:
comment.approve comment.flag comment.remove