On Sunday, March 30, 2014 9:51:06 PM UTC-7, Nicolas Goy wrote:
>
> Given a many_to_many association,
>
> many_to_many :categories
>
> I want to add an accessor for category_ids.
>
> Until now I was using the following code:
>
> def category_ids
> @category_ids || categories_dataset.select_map(:id)
> end
>
> def category_ids=(ids)
> @category_ids = ids
> modified!
> end
>
> def after_save
> super
> if defined?(@category_ids)
> self.remove_all_categories
> Category.where(:id => @category_ids).each do |c|
> self.add_category(c)
> end
> end
> end
>
> I was wondering if there was a better approach.
>
The association_pks plugin handles this for you, though it doesn't defer
the handling until after save. You can use the instance_hooks plugin to do
that:
plugin :association_pks
plugin :instance_hooks
many_to_many :categories
object.after_save{object.category_pks = [1, 2, 3]}
The association_pks plugin is a little faster than the code you used, since
for items that haven't changed, it doesn't delete them just to reinsert
them later.
Thanks,
Jeremy
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