Rails: Chained database query from multiple classes

Question

I have an app that is intended to sort all user articles by identical user fields. An example of this is if a user wanted to see all other user articles from users with a similar occupation. Each user has an occupation (string) field in the database. I've been able to filter all users with identical occupations by using this query:

similar_users = User.where(occupation: current_user.occupation)

I have been unsuccessful at filtering their articles by similar_users. Articles have an author_id which is equal to the user.id.

I've tried chains such as Articles.similar_users, Articles.similar_users.where(author_id: user.id), or Article.all.where(author_id: similar_users.id), but they don't work and rightly so. How would I go about chaining these classes? Is there more effective way, such as using named scopes with lambdas?

In Article.rb

  belongs_to(
  :user,
  class_name: "User",
  foreign_key: :author_id,
  primary_key: :id
  )

In User.rb

has_many(
:articles,
class_name: "Article",
dependent: :destroy
)

user3181113 · Accepted Answer · 2014-03-01 06:12:06Z

2

You have to something like

Article.includes(:user).where("users.occupation = ?", current_user.occupation)

edited Mar 1, 2014 at 6:12

user3181113

7582 gold badges11 silver badges23 bronze badges

answered Mar 1, 2014 at 2:11

Paritosh Piplewar

8,1465 gold badges28 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

12 Comments

Victor Moroz Over a year ago

Have you ever heard about SQL injections?

user3181113 Over a year ago

Yes, I have, but I avoided them because I've heard they pose security threats if someone was able to inject their own code.

Paritosh Piplewar Over a year ago

@VictorMoroz let me know how could you possibly break the above generated sql. I haven't consider anything like data is coming from user-input or so. I would update the answer or delete it. thanks

user3181113 Over a year ago

I tried that code on another repository that functions identically, but with Post instead of Article and I got this error #<#<Class:#<ActiveRecord::Relation::ActiveRecord_Relation_Post:0x0000010475d0a0>>:0x823ae850>

Victor Moroz Over a year ago

Rule of thumb is to assume that string fields can always come from user input. Use placeholders (? or :name), they were created for a reason.

|

Collectives™ on Stack Overflow

Rails: Chained database query from multiple classes

1 Answer 1

12 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

12 Comments

Your Answer

Sign up or log in

Post as a guest

Related