I’ve used Postgres arrays as custom associations before; I’d be willing to help
with this, though I don’t have a ton of experience with the ActiveRecord
codebase.
> On Aug 24, 2017, at 6:31 PM, Michael Giovinco <aegiswi...@gmail.com> wrote:
>
> The subject line is probably a little confusing, so here is an example.
>
> Let's say you have a "person" model that inherits from ActiveRecord::Base.
>
> That person has a list of "sports" that they like and "sport" is also a model
> inheriting from ActiveRecord::Base.
>
> Now, since there are many people and many sports, this is a many-to-many
> relation and you could model it as a join table linking "person" and "sport"
> using a has_many_through relation.
>
> But what I would like to do, is to have an array of "sport_ids" on the
> "person" object. Each id would refer to a "sport", and you also get ordering,
> say if you want the first "sport_id" to point to the person's favorite sport.
>
> I know you can do this, by you have to do all the work yourself.
>
> For example, if you wanted to get the sports for a person, you would write a
> function on "Person" like:
>
> def sports
> Sport.where(id: sport_ids)
> end
>
>
>
> Then you can do:
>
> person.sports
>
>
> and get an array of sport objects. The problem is you will lose the ordering
> of the array here, which might be something you care about. You can try and
> do a fancy order clause to keep the array ordering but it is a little bit
> messy.
>
> But the other problem is that this is inefficient. Say you wanted to get all
> children and what sports they like. You can't do something like:
>
> Person.includes(:sports).where("age < 18")
>
>
>
> You end up with an n+1 query problem because you are stuck doing something
> like:
>
> children = Person.where("age < 18")
> children.each do |child|
> child.sports
> ...
>
> Furthermore, it would great to be able to do things like this:
>
> person.sports << hockey
> person.sports[2] = baseball
>
>
> Anyways, has anyone considered adding a feature like this to ActiveRecord? If
> not, I'm going to work on this because it would be very useful for a couple
> of projects that I am working. I'd greatly appreciate if someone could point
> me in the right direction to get more acquainted with the ActiveRecord
> codebase.
>
> Thanks.
>
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