Ruby on Rails

On 4 September 2014 18:45, Michael Bostler <lists@ruby-forum.com> wrote:
> Hi all,
>
>
> Say I have an article class that has one main tag, but can also be
> associated with multiple secondary tags. Something like schema listed
> below. How can I implement the scope method below?
>
>
> Basically I want one method where I can return ALL articles related to a
> tag, regardless of whether it is a primary tag relationship or secondary
> tag relationship.

You might consider a different schema to that you have shown below, so
that article has_many tags through tag_listings, and in tag_listings
have a flag to indicate a primary tag (or not). Then you get the
primary tag by selecting the tag with that flag set. Then the problem
you have asked about becomes not a problem (which is the best sort).
Still not ideal I know, as you have to guard against the possibility
of inadvertently ending up with multiple primary tags. Perhaps there
is a better solution.

Colin

>
>
> Many Thanks!
>
>
> class Article < ActiveRecord::Base
> belongs_to :primary_tag,
> :class_name => "Tag"
>
> has_many :secondary_tag_listings
>
> has_many :secondary_tags,
> :through => :secondary_tag_listings,
> :class_name => "Tag"
>
> scope :all_with_tag, lambda { |tag_name|
> # TODO: how to find all with either primary OR secondary tags
> # as tag_name?
> }
> end
>
>
>
>
> class SecondaryTagListings < ActiveRecord::Base
> belongs_to :article
> belongs_to :tag
> end
>
>
>
>
> class Tag < ActiveRecord::Base
> has_many :primary_articles,
> :class_name => "Article"
>
> has_many :secondary_tag_listings
>
> has_many :secondary_articles,
> :through => :secondary_tag_listings,
> :class_name => "Article"
> end
>
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