I have a Rails application, that uses callbacks a lot.. so that I have quite a few functions getting called :after_create and :after_commit in multiple models.
I wonder if the way I am doing it right now is the best.
Basically I have the following scenario:
Class Parent < ActiveRecord::Base
has_many :children
after_create :first_function
after_commit :last_function
def first_function
if !self.processed?
self.children.create(:name => "Richard The Lion Heart")
self.processed = true
self.save!
end
end
def last_function
if self.processed?
if !self.processing?
self.process
self.save!
self.processing = true
self.save!
end
end
end
end
So you can see the whole thing depends on some strange dual boolean checks because otherwise second_function is getting called every time the model is being updated and it can be updated by the function itself and so the function is getting called repetitively.
Overall it leads me to the case where I have to introduce a new boolean check for every callback to fire off. It works but I don't see it as elegant. What am I missing?
You should be able to rewrite that code -- something like this? Of course your real code probably has some additional complexity -- ALSO: this code is untested.
Class Parent < ActiveRecord::Base
has_many :children
# only called when a new record is created
after_create :first_function
# only called for updates, not new records, should still be inside the current transaction
after_update :last_function
private
def first_function
self.children.create(:name => "Richard The Lion Heart")
# don't call save in here, already in a transaction
end
def last_function
self.process
# don't call save in here, already in a transaction
end
def process
# doing stuff ....
self.children[0].update_attribute(:name, "Beowulf")
end
end
http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html
That’s a total of twelve callbacks, which gives you immense power to react and prepare for each state in the Active Record life cycle. The sequence for calling Base#save for an existing record is similar, except that each _create callback is replaced by the corresponding _update callback.
usage
p = Parent.new(:foo => "bar")
p.save
p.children[0].name
# => "Richard The Lion Heart"
p.update_attributes(:baz => "fud")
p.children[0].name
# => Beowulf
ActiveRecord callbacks from rails console (with awesome_print ap)
> ap ActiveRecord::Callbacks::CALLBACKS
[
[ 0] :after_initialize,
[ 1] :after_find,
[ 2] :after_touch,
[ 3] :before_validation,
[ 4] :after_validation,
[ 5] :before_save,
[ 6] :around_save,
[ 7] :after_save,
[ 8] :before_create,
[ 9] :around_create,
[10] :after_create,
[11] :before_update,
[12] :around_update,
[13] :after_update,
[14] :before_destroy,
[15] :around_destroy,
[16] :after_destroy,
[17] :after_commit,
[18] :after_rollback
]
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