Get an array of many objects associations

Question

I didn't know exactly how to find an understandable title so I'll try my best to explain my problem.

I have 2 models: - Country translatable with globalize, with a name and many regions - Region belongs_to country

What I would like to do is geting an array of all regions form an array of countries.

E.g.

Country.all.regions
Country.with_translations(I18n.locale).order("country_translations.name asc").regions

There is an easy way to get this array ?

Thank you its exactly what I was looking for. I answered with your answer for others ! — Ugo Mare, Jan 27 '15 at 12:02

score 5 · Accepted Answer · answered Jan 27 '15 at 12:24

5

The @Octopus-Paul solution works, but it has n+1 queries problem. To avoid it, use the includes method.

Country.includes(:regions).all.map {|country| country.regions }.flatten

answered Jan 27 '15 at 12:24

Rodrigo

5

One nice trick you can do here is use `.flat_map{ ... }` instead of `.map{ ... }.flatten`. – antinome Apr 24 '15 at 16:35
Another thing you can do to clean it up is: `Country.includes(:regions).all.flat_map(&:regions)` – Devchris Apr 14 '21 at 12:07

score 0 · Answer 2 · answered Jan 27 '15 at 12:01

0

From @Octopus-Paul:

Country.all.map {|country| country.regions }.flatten

answered Jan 27 '15 at 12:01

Ugo Mare

Edison Arango · Answer 3 · 2019-07-24T21:41:06.703

0

Just search for the regions that match your list of countries:

countries = Country.all
regions = Region.where(country: countries)

edited Jul 24 '19 at 21:41

answered Jul 16 '19 at 02:32

Edison Arango

I know this is pretty explicit, but try to add a bit more text to explain why your solution is the good one – Olympiloutre Jul 16 '19 at 02:54

3 Answers3