Check if record exists from controller in Rails

by

Why your code does not work?

The where method returns an ActiveRecord::Relation object (acts like an array which contains the results of the where), it can be empty but it will never be nil.

Business.where(id: -1) 
 #=> returns an empty ActiveRecord::Relation ( similar to an array )
Business.where(id: -1).nil? # ( similar to == nil? )
 #=> returns false
Business.where(id: -1).empty? # test if the array is empty ( similar to .blank? )
 #=> returns true

How to test if at least one record exists?

Option 1: Using .exists?

if Business.exists?(user_id: current_user.id)
  # same as Business.where(user_id: current_user.id).exists?
  # ...
else
  # ...
end

Option 2: Using .present? (or .blank?, the opposite of .present?)

if Business.where(:user_id => current_user.id).present?
  # less efficiant than using .exists? (see generated SQL for .exists? vs .present?)
else
  # ...
end

Option 3: Variable assignment in the if statement

if business = Business.where(:user_id => current_user.id).first
  business.do_some_stuff
else
  # do something else
end

This option can be considered a code smell by some linters (Rubocop for example).

Option 3b: Variable assignment

business = Business.where(user_id: current_user.id).first
if business
  # ...
else
  # ...
end

You can also use .find_by_user_id(current_user.id) instead of .where(...).first

Best option:

  • If you don’t use the Business object(s): Option 1
  • If you need to use the Business object(s): Option 3

More Related Contents:

  1. Eager load polymorphic
  2. Rails order by results count of has_many association
  3. How to chain scope queries with OR instead of AND?
  4. When to use a “has_many :through” relation in Rails?
  5. Rails 3: Get Random Record
  6. Setting session timeout in Rails 3
  7. Alias for column names in Rails
  8. ActiveRecord Find By Year, Day or Month on a Date field
  9. Rails 3 devise, current_user is not accessible in a Model ?
  10. Rails 3, has_one / has_many with lambda condition
  11. Rails 3 – select with Include?
  12. belongs_to through associations
  13. Validate uniqueness of multiple columns
  14. Rails – Validate Presence Of Association?
  15. How to implement bulk insert in Rails 3
  16. PGError: ERROR: aggregates not allowed in WHERE clause on a AR query of an object and its has_many objects
  17. Specifying column name in a “references” migration
  18. Rails: Order with nulls last
  19. Why do routes with a dot in a parameter fail to match?
  20. Rails 5: ActiveRecord OR query
  21. Ruby on Rails. How do I use the Active Record .build method in a :belongs to relationship?
  22. rake db:schema:load vs. migrations
  23. How to test for (ActiveRecord) object equality
  24. Bulk Insert records into Active Record table
  25. What are the brackets [5.1] after ActiveRecord Migration and how does it work? [duplicate]
  26. Convert UTC to local time in Rails 3
  27. Scope with join on :has_many :through association
  28. Rails form_for :remote=>true is not calling js method
  29. Remote mysql database on Heroku app
  30. Ruby on rails 4 app does not work in iframe

Leave a Comment