CODEWITHSUNDEEP
sqlrubyactiverecordruby-on-rails-3.1
user1051849
user1051849

Reputation: 2337

ruby rails - getting a collection of objects from a collection of foreign keys

Easy one i think/hope... I have a query that returns a list of 20 unique foreign keys:

@results   = Report.select("distinct user_id").where("datetime_utc >= ? AND datetime_utc <= ?",@utc_time_slot , @utc_time_slot_end).order("score DESC, quality DESC").limit(20)

this returns an array (ActiveRecord::Relation class):

[#<Report user_id: 803>, #<Report user_id: 809>, #<Report user_id: 806>, #<Report user_id: 801>, #<Report user_id: 830>, #<Report user_id: 860>, #<Report user_id: 858>, #<Report user_id: 856>, #<Report user_id: 854>, #<Report user_id: 852>, #<Report user_id: 851>, #<Report user_id: 850>, #<Report user_id: 849>, #<Report user_id: 846>, #<Report user_id: 859>, #<Report user_id: 866>, #<Report user_id: 2022>, #<Report user_id: 863>, #<Report user_id: 862>, #<Report user_id: 838>]

What do i need to do with this @results array to extract the collection of users form the users table that the user_id list refers to (in the same order)?

Thanks!

Upvotes: 0

Views: 1655

Answers (4)

UncleGene
UncleGene

Reputation: 2142

You have two options for preserving order. First - eager load users in original query. In this case

users = @results.map(&:user)

Second - reorder on ruby side

idx = User.find(@results.map(&:user_id)).index_by(&:id)
users = @result.map{|r| idx[r.use_id]}

Upvotes: 1

josephrider
josephrider

Reputation: 943

How about:

users = @results.collect(&:user)

Upvotes: 1

cvshepherd
cvshepherd

Reputation: 3997

User.find(@results.map(&:user_id))

Upvotes: 0

codevoice
codevoice

Reputation: 474

Hej, First of all you need to prepare the array of user_ids. it should look like this [209, 902, ..., 890] (you can use map or collect method to do that) then just build sql query like that:

User.where(:id=>user_ids)

where the user_ids is prepared array

Upvotes: 0

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