I have the following classes:
class AwardBase
class AwardOne < AwardBase
class Post < ActiveRecord::Base
The Post is an ActiveRecord, and the Award has a can_award? class method
which takes a post object and checks to see if it meets some criteria.
If
yes, it updates post.owner.awards.
I know I can do this using an Observer pattern (I tested it and the code
works fine). However, that requires me to add additional code to the
model.
I’d like not to touch the model at all if possible. What I’d like to do
is
run the Award checks like this (the trigger will be invoked at class
load
time):
class AwardOne < AwardBase
trigger :post, :after_save
def self.can_award?(post)
...
end
end
The intention with the above code is that it should automatically add
AwardOne.can_award? to Post’s after_save method
So essentially what I’m trying to do is to get the above code to be
equivalent to:
class Post < ActiveRecord::Base
after_save AwardOne.can_award?(self)
...
end
which is basically:
class Post < ActiveRecord::Base
after_save :check_award
def check_award
AwardOne.can_award?(self)
end
end
How can I do this without modifying the Post class?
Here’s what I’ve done (which does not appear to work):
class AwardBase
def self.trigger (klass, active_record_event)
model_class = klass.to_class
this = self
model_class.instance_eval do
def award_callback
this.can_award?(self)
end
end
model_class.class_eval do
self.send(active_record_event, :award_callback)
end
end
def self.can_award? (model)
raise NotImplementedError
end
end