Question

I’d like to use an if statement to check if the value in a Postgres DB table is unique. If unique, then do something, if not unique, do something else. Here’s what the pseudo code would look like in Ruby on Rails.

if validates_uniqueness_of :number == "true"
    puts "this value is unique and should be added to the DB"
else 
    puts "this value is not unique and should not be added to the DB"
end

Can this type of logic be implemented in the model or controller? If yes, which is the better way to go? If no, what should I do instead? Also, what would the syntax look for something like this?

Thanks guys!

Answer 1

You can use the exists? method to check whether a record is in the database already. It can take a hash of fields you want to search on:

before_create :do_something_if_unique

def do_something_if_unique
  if self.class.exists?(number: number)
    # there is a record that exists with this number
  else
    # there are no records that exist with this number
  end
end