Hi,
first of all I would like to wish a happy new year to all the list members.
Here is my problem. I have a model class where I need to overwrite an
accessor method in order to add some extra behaviour:
class LineItem < ActiveRecord::Base
belongs_to :item, :polymorphic => true
# add_item
#
def item=(item)
write_attribute(:item, item)
self.price = item.price
end
# item
#
def item
read_attribute(:item)
end
end
The problem is that when I overwrite the item= method, the item_id and
item_type attributes aren''t stored in the database when I save the
object so the associated item is missed. I know I could manually set the
item_id and item_type values with something like this:
def item=(item)
write_attribute(:item, item)
self.price = item.price
self.item_id = item.id
self.item_type = item.class.to_s
end
but the problem with this solution resides on that the given item
probably has no id as it should handled as a new record too.
Is there any way I could use the default association behaviour(that is
to automatically set the item_id and item_type attributes and saving the
item first when necessary) and still being able to overwrite the writer
method too? I also tried it by aliasing the item= method but with no
success.
Thanks in advance.
--
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Borja Martín wrote:> Hi, > first of all I would like to wish a happy new year to all the list members.Thank you Borja.> Here is my problem. I have a model class where I need to overwrite an > accessor method in order to add some extra behaviour:Look here: http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/4fe057494c6e23e8 -- We develop, watch us RoR, in numbers too big to ignore. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Thanks Mark, I solved it by using the alias_method_chain as you suggested:
class LineItem < ActiveRecord::Base
belongs_to :item, :polymorphic => true
def item_with_price_check=(item)
self.item_without_price_check = item
self.price = item.price
end
alias_method_chain :item=, :price_check
end
Regards
Mark Reginald James escribió:> Borja Martín wrote:
>
>> Hi,
>> first of all I would like to wish a happy new year to all the list
members.
>>
>
> Thank you Borja.
>
>
>> Here is my problem. I have a model class where I need to overwrite an
>> accessor method in order to add some extra behaviour:
>>
>
> Look here:
http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/4fe057494c6e23e8
>
>
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Borja Martín wrote:> Hi, > first of all I would like to wish a happy new year to all the list > members. > > Here is my problem. I have a model class where I need to overwrite an > accessor method in order to add some extra behaviour: > > class LineItem < ActiveRecord::Base > > belongs_to :item, :polymorphic => true > > # add_item > # > def item=(item) > write_attribute(:item, item) > self.price = item.price > end > > # item > # > def item > read_attribute(:item) > end > end >What you need are association callbacks. The following is from the ActiveRecord::Association::ClassMethods Page in the RDoc: Association callbacks Similiar to the normal callbacks that hook into the lifecycle of an Active Record object, you can also define callbacks that get trigged when you add an object to or removing an object from a association collection. Example: class Project has_and_belongs_to_many :developers, :after_add => :evaluate_velocity def evaluate_velocity(developer) ... end end Its possible to stack callbacks by passing them as an array. Example: class Project has_and_belongs_to_many :developers, :after_add => [:evaluate_velocity, Proc.new { |p, d| p.shipping_date = Time.now}] end Possible callbacks are: before_add, after_add, before_remove and after_remove. Should any of the before_add callbacks throw an exception, the object does not get added to the collection. Same with the before_remove callbacks, if an exception is thrown the object doesnt get removed. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---