In Rails 4 you should be able to do:
class Post
has_many :comments, -> { visible }
end
On 21/05/13 23:41, Caleb Thompson wrote:
> I'm considering implementing a feature by which a collection
> association might limit the results.
>
> By default, a collection association returns all values where the
> foreign key on the `belongs_to` or `has_and_belongs_to` model matches
> the parent object's primary key. These results can be filtered using the
> `conditions` option, but that requires that other models have knowledge
> of the parent model's table structure.
>
> The feature I'm proposing is to add a `scope` option to collection
> associations which takes a symbol representing a scope (or class mehtod)
> defined on the associated model class.
>
> A basic example would look like this:
>
> class Comment
> belongs_to :post
>
> def self.visible
> where(deleted_at: nil)
> end
> end
>
> class Post
> has_many :posts, scope: :visible
> end
>
> In the above example, `post.comments` would return `Comment` instances
> whose `post_id = post.id` and whose `deleted_at = NULL`, providing basic
> soft-deletion functionality.
>
> While the same effect could be achieved with a declaration such as
> `has_many :posts, conditions: ['deleted_at = ?', nil]`, that betrays
> knowledge of the implementation of deletion on `Post` and would break if
> the implementation were changed to a boolean value for deletion rather
> than a timestamp field.
>
> If I were to work on adding this functionality into ActiveRecord, is it
> something that core might entertain merging?
>
> Thank you,
>
> Caleb Thompson
>
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