CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4activerecord
Alec Sanger
Alec Sanger

Reputation: 4562

Selecting only associations between engines

I need to grab all users that have an application. User is part of my core engine, which is used by many other engines. I'd like to keep User unaware of what is using it, which is why I don't want to add has_many :training_applications in my User model.

Here are the classes

module Account
  class User < ActiveRecord::Base

  end
end


module Training
  class TrainingApplication < ActiveRecord::Base

    belongs_to :user, class: Account::User

  end
end

The following obviously won't work because User has no concept of TrainingApplication:

Account::User.joins(:training_application).distinct

Is there an elegant way to return a distinct collection of User objects that are associated with a TrainingApplication?

What I landed on as a quick solution is 

Account::User.where(id: Training::TrainingApplication.all.pluck(:user_id))

but I'm thinking that there's a better solution.

Upvotes: 0

Views: 22

Answers (1)

SHS
SHS

Reputation: 7744

In case there is no way you can add a has_many :training_applications association to the User, the following should be suitable solutions:

You could type up a joins string yourself:

t1 = Account::User.table_name
t2 = Training::TrainingApplication.table_name

Account::User.
joins("INNER JOINS #{t2} ON #{t2}.user_id = #{t1}.id").
group("#{t1}.id")

For the sake of variety, let me cover the subquery method as well:

Account::User.where("id IN (SELECT user_id FROM #{t2})")

I would go with the joins method but I believe both solutions will be faster than your current implementation.

Upvotes: 1

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