Let's assume a very simple Payment class like this:
class Payment
include AASM
aasm do
state :created
state :paid
state :refunded
event :pay do
transitions from :created, to :paid
end
end
end
So one would call payment.pay to trigger the payment, making the appropriate API Calls.
It's very important that the transition from created to paid only happens if the payment actually succeeds.
1) I would assume the API Calls should be put in a before callback in the :pay event, but that would not halt the transition if the API call was unsuccessful (let's assume the API call does NOT raise an exception, it just returns a status).
2) I then thought that I should combine the before callback with a guard; use the before callback to call the API, and set it's result on the model (using an attr_accessor for instance). Then the guard would only allow it transition from the created to paid state if the payment was successful.
Is that the idiomatic way of handling such an event transition in a state machine with aasm? I read all stack overflow's questions tagged aasm and the gem documentation and still have questions about what's the best way to make these safe transitions.
