callbacks and validations

[obrie]

qoobaa opened this issue

@@@ ruby
state_machine :initial => :first do
event :boom
transition :first => :second
end

state :second
validate :something # validation fails
end

after_transition :boom, :do => lambda { puts "BOOM!!!" }
@@@

result:

@@@

object_with_state_machine.boom!
BOOM!!!
StateMachine::InvalidTransition: Cannot transition state via :boom from :first
@@@

I think it’s not expected behavior, it causes a lot of problems in my app.

original LH ticket

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[obrie]

To me, this is expected behavior. By defining a validation for the :second state, you’re indicating that any object in that state must pass that validation. As a result, when you attempt to transition from :first to :second via :boom, the validations for :second will be run.

Can you expand on this bug?

[obrie]

qoobaa commented

The problem was, that I had to check if the transition is valid or not in associated model validation. I tried to find a workaround, for instance to call a method in associated model after valid transition, but in this case it’s impossible. I’ve also tried to use after_update callback:
@@@ Ruby
state :second do
after_update { puts "BOOM!!!" }
end
@@@
... but it doesn’t work at all. Finally I use event methods with bangs to check the transition:

@@@ Ruby
class ChildModel < ActiveRecord::Base
belongs_to :parent_model
after_update { parent_model.boom! }
end
@@@

If transition fails, exception is thrown and transaction is rolled back. That’s enough for me at the moment.

[obrie]

qoobaa commented

Formatting problems, once again:

The problem was, that I had to check if the transition is valid or not in associated model validation. I tried to find a workaround, for instance to call a method in associated model after valid transition, but in this case it’s impossible. I’ve also tried to use after_update callback:

@@@ ruby
state :second do
after_update { puts "BOOM!!!" }
end
@@@

... but it doesn’t work at all. Finally I use event methods with bangs to check the transition:

@@@ ruby
class ChildModel < ActiveRecord::Base
belongs_to :parent_model
after_update { parent_model.boom! }
end
@@@

If transition fails, exception is thrown and transaction is rolled back. That’s enough for me at the moment.

[obrie]

If you need to do validation on the availability of an event, you can use something like:

@@@ ruby
parent_model.can_boom?
@@@

You can see all of the various instance methods that are generated for an Event in the docs. They are currently:

• can_{name}?
• {name}_transition
• {name}(run_action = true)
• {name}!(run_action = true)

Also, the latest updates on github might help you, specifically the attribute-based events: http://github.com/pluginaweek/state_machine/commit/2122d327aa835d47a71ff3bd750cfaa525e0cbb5

Feel free to re-open the ticket if you have additional feedback.