[LRUG] Better idiom for this?

[Ash Berlin]

ActiveRecord has a thing where you can pass an record into a condition and it automatically converts to the PK, using a method called something like 'to_param' (but can't remember the exact name.)

The net effect is you don't have to treat int ids different to objects:

> u = User.first
=> #<User id: 1>
> User.where(:id.not_in => [ u ] ).to_sql
=> "SELECT `users`.* FROM `users` WHERE `users`.`id` NOT IN (1)"

(I'm using metawhere to get the :id.not_in syntax. Old 3.0 project.)

-ash

On 28 Feb 2013, at 11:41, Michael Pavling <pavling at gmail.com> wrote:

> Hiya,
> 
> Ruby (well... Rails) question...
> 
> I frequently have a need to return a collection of model objects, which exclude some amount of records (by ID)
> 
> I want the flexibility to be able to do the exclusion on either instances of the model, or just ids (as strings or integers).
> 
> I have previously used a named scope, and currently (3.2) have started to use a class-method, but it's looking a little clunky/smelly to me... 
> 
>   class Foo < ActiveRecord::Base
>     class << self
>       def excluding(*objects)
>         objects = objects.flatten.delete_if(&:blank?)
>         object_ids = objects.map { |object| object.respond_to?(:to_i) ? object.to_i : object.id }
>         object_ids.any? ? where(['id NOT IN (?)', object_ids]) : scoped
>       end
>     end
>   end
> 
>   # so I can now call:
>   Foo.excluding(some_foo_object)
>   Foo.excluding(some_foo_object, another_foo_object)
>   Foo.excluding([1,2,3])
>   Foo.excluding(params[:foo_ids_to_exclude])
>   etc.
> 
> OOI does anyone have a better idiom for this approach?
> 
> M
> 
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