Use a string literal value in a model association

[TSMMark]

Setting aside db schema design concerns... is it possible to define a model association where the FK value is a string literal defined in Ruby at definition time?

I tried this but i think it is trying to call a method by name of the value provided of slug:

base.many_to_one :network, key: Sequel.lit(base.slug), primary_key: :slug

e.g. slug = "youtube"

undefined method `youtube' 

[jeremyevans]

By default, for normal association loading, Sequel calls methods on the receiver to get the values used in the association query. If you want a static string literal, you could try defining a method that returns it. I'll admit I'm not sure what value there would be in having an association defined that way, unless you were using some other approach to make the association receiver-specific. Maybe it would help to provide a more complete example showing what you want?

[TSMMark]

Thanks for your quick and valuable response as always @jeremyevans

try defining a method that returns it

That sounds reasonable! But would that work for dataset things, like association_join?

I'll post a more complete example in a moment

[TSMMark]

Simplified the schemas and naming for the example, but it's something like this:

networks
id	PK
slug	unique slug consistent across environments
...

youtube_accounts
id	PK
...

facebook_accounts
id	PK
...

We want YoutubeAccount many_to_one Network on a constant value "youtube", which is the value of slug for the network record corresponding to youtube.
And FacebookAccount many_to_one Network on constant "facebook".
Etc, for several more *_account tables

[jeremyevans]

Does the pk in youtube_accounts match networks? Otherwise, I don't think there is enough information, since the foreign key information is not provided.

You could also try posting the SQL you want the association query to generate.

[TSMMark]

The FK is essentially the slug. There is 1 record in networks for each slug; each *accounts model should be associated with 1 static slug. Will post example SQL generated next

[TSMMark]

I think the SQL would be pretty simple, just WHERE on the slug value for that model:

YoutubeAccount.sample.network # => #<Network @values={:id=>1, :slug=>"youtube"}>
# => SELECT * FROM "networks" WHERE ("slug" = 'youtube') LIMIT 1

FacebookAccount.sample.network # => #<Network @values={:id=>2, :slug=>"facebook"}>
# => SELECT * FROM "networks" WHERE ("slug" = 'facebook') LIMIT 1

[jeremyevans]

It doesn't make sense to use an association for this, as all instances of YoutubeAccount will have the same return value, and all instances of FacebookAccount will have the same return value. You can do it if you really want to:

many_to_one :network, dataset: ->(r){r.associated_class.where(slug: 'youtube')}

If the networks are not being modified, I would recommend constants:

Network::Youtube = Network[slug: 'youtube']

class YoutubeAccount
  def network = Network::Youtube
end

[TSMMark]

Yeahh I understand it's not a usual kind of association. I'll just continue using static methods similar to your suggestion. Thanks!