Rails core - Feb 2007 - Per activerecord object callbacks (aka: should I have gone to bed hours ago?)

First of all, I should have gone to bed a long time, so please be
forgiving with regards to what will follow :)

So I''ve been working all day on a rails project that needs to go out
soon, and I thought I would try to refactor a has_many relationship to
a has_and_belongs_to_many relationship (using has_many :through).
However, I then realized that I would loose a lot of the simple beauty
of my code because has_many :through doesn''t support the create
method.

I was messing around with this, and I thought, can''t we add a
per-object callback system as well as a per class callback system.
Then we could add create methods to has_many :through.

Here''s my super hacked "proof of concept" (if it can even be
called that).

http://pastie.caboo.se/37802

and a little extract from the console demonstrating it.
>> t = Taggable.create
=> #<Taggable:0x1462de0 @attributes={"name"=>nil,
"id"=>1},
@new_record_before_save=true, @errors=#<ActiveRecord::Errors:0x2810d2c
@base=#<Taggable:0x1462de0 ...>, @errors={}>, @callbacks={},
@new_record=false>
>> tag = t.tags.create
=> #<Tag:0x27d5b50 @attributes={"name"=>nil},
@errors=#<ActiveRecord::Errors:0x27bd5f0 @base=#<Tag:0x27d5b50 ...>,
@errors={"name"=>["can''t be blank"]}>,
@callbacks={:after_save=>#<Proc:0x02639800@./script/../config/../config/../lib/am_i_insane.rb:28>},
@new_record=true>
>> tag.name = "Hello"
=> "Hello"
>> Tagging.count
=> 0
>> tag.save
=> true
>> Tagging.count
=> 1

Any thoughts on this? Am I missing some implications or anything? I
definitely not am an expert of the ruby on rails code...

alright, I''m off to bed.
-carl

-- 
EPA Rating: 3000 Lines of Code / Gallon (of coffee)

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On Feb 4, 2007, at 12:15 PM, Carl Lerche wrote:
> I was messing around with this, and I thought, can''t we add a
> per-object callback system as well as a per class callback system.
> Then we could add create methods to has_many :through.
Whi don''t you just define create on the association

has_many ... do
	def create
		...
	end
end
-- 
Julian ''Julik'' Tarkhanov
please send all personal mail to
me at julik.nl



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On 2/4/07, Julian Tarkhanov <listbox@julik.nl>
wrote:
>
>
> On Feb 4, 2007, at 12:15 PM, Carl Lerche wrote:
>
> > I was messing around with this, and I thought, can''t we add a
> > per-object callback system as well as a per class callback system.
> > Then we could add create methods to has_many :through.
>
> Whi don''t you just define create on the association
>
> has_many ... do
>         def create
>                 ...
>         end
> end
I''m not exactly sure how defining create on the association would work
for a has_many :through association. There is the join model that has
to be created. Currently, there is a create! method defined for
has_many :through associations. The create! method will throw an error
if validations fail. This is necessary because currently, the join
object has to be created right away.

However, if per-object callbacks are implemented, create is
possible... so is build. I don''t know if that makes sense. I will try
to work up some better code.

-carl


-- 
EPA Rating: 3000 Lines of Code / Gallon (of coffee)

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