Rails activerecord query using select but return collection

Question

I want to perform a query that selects all users that are "allowed" to interact according to the following method:

User.rb

def allowed?(other_user)
  self.friends.include?(other.user) || self.followers.include?(other_user)
end

The problem is that .select { |user| ... } is returning an array, not a collection. How should I write the query correctly so further database queries can be appended (such as limit or order)?

users controller

@user = current_user

@users = User.select { |user| @user.allowed?(user) }
             .limit(100)
             .order(created_at: :desc)
             .paginate(page: params[:page])

Sebastián Palma · Accepted Answer · 2019-08-31 22:00:53Z

2

The allowed? method can be written as a class method as:

def self.allowed(other_user)
  User
    .joins(:friends, :followers)
    .where(
      'friends.user_id = :user_id OR followers.user_id = :user_id',
      user_id: other_user.id
    )
end

Which uses joins to specify the relationships of both friends and followers tables with users.

That makes allowed easily chainable, so you can have your allowed? method as a predicate in case you need it:

def self.allowed?(other_user)
  User.allowed(other_user).exists?
end

So you can do:

User
  .allowed(@user)
  .limit(100)
  .order(created_at: :desc)
  .paginate(page: params[:page])

edited Aug 31, 2019 at 22:00

answered Aug 31, 2019 at 21:32

Sebastián Palma

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