Question

UPDATED I’m using Devise 1.4.9 for authentication and my Devise-generated User model doesn’t seem to be catching the exceptions being thrown by the DB when I try to create a new user with an email address that already exists in the DB. After following cicloon’s suggestion (see response below), my code to create a new user is…

class Api::RegistrationsController < Api::BaseController

  respond_to :json

  def create
    user = User.new(params[:user])
    user.ensure_authentication_token! 

    if user.valid?
        user.save
        render :json=> user.as_json(:auth_token=>user.authentication_token, :email=>user.email, :user_id=>user.id), :status=>201
        return
    else
        warden.custom_failure!
        render :json=> user.errors, :status=>422
    end
  end
end

The Devise-generated migration includes an index for the email attribute, including uniqueness validation…

add_index :users, :email, :unique => true

And here’s the user model…

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable, :token_authenticatable

  attr_accessible :email, :password, :password_confirmation, :remember_me, :authentication_token 

  validates_uniqueness_of :email

  def ensure_authentication_token!   
    reset_authentication_token! if authentication_token.blank?   
  end  

  def as_json(options={})
    super(:only => [:email, :authentication_token, :id])
  end

end

…I would like the database to raise an error during save if the specified email address already existed in the DB, have Rails catch it and execute the else block of code to return a 422 and description of the problem. It doesn’t, instead I get an SQLException error and a crash…

ActiveRecord::StatementInvalid (SQLite3::ConstraintException: constraint failed: INSERT INTO "users" ("authentication_token", "created_at", "current_sign_in_at", "current_sign_in_ip", "email", "encrypted_password", "last_sign_in_at", "last_sign_in_ip", "remember_created_at", "reset_password_sent_at", "reset_password_token", "sign_in_count", "updated_at") VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)):
  app/models/user.rb:33:in `ensure_authentication_token!'
  app/controllers/api/registrations_controller.rb:7:in `create'

How can I get my code to return a 422 with a description of the error?

Thanks so much in advance for your wisdom!

Answer 1

I read your post again, now I see what’s happening there. You have a database index, and Rails is not aware of that, so when you make @user.save the database throws an exception which is not captured Rails side.

That said, you have two choices:

1.) Capture the exception in Rails:

begin
  user.save
  render :json=> user.as_json(:auth_token=>user.authentication_token, :email=>user.email, :user_id=>user.id), :status=>201

rescue
  warden.custom_failure!
  render :json=> user.errors, :status=>422
end

2.) Add the validation to your model and check for user.valid?:

On your user model:

validates_uniqueness_of :email

On your controller:

  if user.valid?
      user.save
      render :json=> user.as_json(:auth_token=>user.authentication_token, :email=>user.email, :user_id=>user.id), :status=>201
      return
  else
      warden.custom_failure!
      render :json=> user.errors, :status=>422
  end