Question

Is there a method to save an object but return the object if it fails the validation_uniqueness_of for a given field? For example, I have the following:

class User
  has_many :words
...
end

class Word
  belongs_to :user
  validates_uniqueness_of :title
...
end  

And I have a situation where I want to either return the Word object if the user has already saved this word, or return the newly saved word object. I am finding myself checking if the word object exists through my own search and then performing a save if not:

existing_word = find_by_word_and_user_id(word, user)
!existing_word.nil? ? existing_word : user.words.create({:word => word})

But I feel like if the user does not have the word saved, rails is going to perform a redundant search for the title uniqueness validation after my check and I was wondering if I could just do the save and return the already existing object that rails finds for the validation.

Answer 1

You might be interested in #find_or_create_by_word_and_user, another of ActiveRecord’s magic methods:

obj = Word.find_or_create_by_word_and_user(word, user)

# Preferred way
obj = user.words.find_or_create_by_word(word)

This will do 2 database requests anyway: there’s no way around that. Also, if your Word instance has more validation that you’ve shown us, the create will fail, because #find_or_create_by does not allow passing more attributes.

For all the details on the dynamic finder methods, search for “Dynamic attribute-based finders” on http://api.rubyonrails.org/classes/ActiveRecord/Base.html.