In my app a User can create a Business. When they trigger the index action in my BusinessesController I want to check if a Business is related to the current_user.id:
new action. I was trying to use this:
if Business.where(:user_id => current_user.id) == nil # no business found end But it always returns true even when the business doesn't exist...
How can I test if a record exists in my database?
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 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:
Business object(s): Option 1Business object(s): Option 3
blank?.first before .blank? ;)In this case I like to use the exists? method provided by ActiveRecord:
Business.exists? user_id: current_user.id 
with 'exists?':
Business.exists? user_id: current_user.id #=> 1 or nil with 'any?':
Business.where(:user_id => current_user.id).any? #=> true or false If you use something with .where, be sure to avoid trouble with scopes and better use .unscoped
Business.unscoped.where(:user_id => current_user.id).any? 
ActiveRecord#where will return an ActiveRecord::Relation object (which will never be nil). Try using .empty? on the relation to test if it will return any records.
When you call Business.where(:user_id => current_user.id) you will get an array. This Array may have no objects or one or many objects in it, but it won't be null. Thus the check == nil will never be true.
You can try the following:
if Business.where(:user_id => current_user.id).count == 0 So you check the number of elements in the array and compare them to zero.
or you can try:
if Business.find_by_user_id(current_user.id).nil? this will return one or nil.
business = Business.where(:user_id => current_user.id).first if business.nil? # no business found else # business.ceo = "me" end I would do it this way if you needed an instance variable of the object to work with:
if @business = Business.where(:user_id => current_user.id).first #Do stuff else #Do stuff end Something new to try (:
Assign a variable or return
return unless @business = Business.where(user_id: current_user.id).first Method would exit at this point if there are no businesses found with current user's ID, or assigns instance variable @business to the first business object.
wherewill return an empty array if there are no records. And[]doesn't equalnilunless Business.find_by_user_id(current_user.id)?