Check if record exists from controller in Rails

Question

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    If yes  display the business   If no  redirect to the new action     I was trying to use this   if Business where  user id   gt  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

User · Answer

I would do it this way if you needed an instance variable of the object to work with   if  business   Business where  user id   gt  current user id  first    Do stuff else    Do stuff end

User · Answer

business   Business where  user id   gt  current user id  first if business nil    no business found else   business ceo    me  end

User · Answer

When you call Business where  user id   gt  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   gt  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

User · Answer

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       gt  returns an empty ActiveRecord  Relation   similar to an array   Business where id  -1  nil      similar to    nil        gt  returns false Business where id  -1  empty    test if the array is empty   similar to  blank        gt  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   gt  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   gt  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

User · Answer

In this case I like to use the exists  method provided by ActiveRecord   Business exists  user id  current user id

User · Answer

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

User · Answer

with  exists     Business exists  user id  current user id    gt  1 or nil   with  any     Business where  user id   gt  current user id  any     gt  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   gt  current user id  any

[ruby-on-rails] Check if record exists from controller in Rails

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