State::Notifier

gem 'state-notifier'

$ bundle

$ gem install state-notifier

`notify_targets(method_name)` will call `<class_name>_<method_name>` on
every target that supports it (i.e. `responds_to?`). For example, calling
`notify_target(:foo)` on an `Event` object will call `event_foo` on
supporting targets.

`notify_targets` is automatically called with `:created` and `:updated` in
`after_create` and `after_update` respectively.

For classes with a state machine the following calls are made:

`<event_name>` is notified every time.

Additionally, if the new state is different from the previous one, we also
get those 3 notifications:

- `state_changed`
- `<target_state>`
- `<event_name>_<target_state>`
- `<source_state>_<target_state>`

class Event
  belongs_to :provider, ...
  has_many :participants, ...

  include State::Notifier
  notification_targets :provider, :participants, EventMailer

  state_machine do
    ...
    state :canceled

    event :cancel do
      transition all => :canceled
    end
  end

  def foo
    notify_targets :foo
  end
end

class User
  def event_created
    # called for provider when event created (no participants yet)
  end

  def event_foo
    # custom event
  end

  def event_cancel
    # called on event 'cancel'
  end

  def event_canceled
    # called when transitioning into 'canceled' state.
  end
end