Ruby on Rails Active Record return value when create fails?

Question

I am new to ruby on rails and having trouble getting this work. Basically I have a user registration page which has a password confirmation. In the User class I have the followi

Answer 1

The answer is the ActiveRecord object. The official source code shows that create return the object if it succeeds or fails:

# File activerecord/lib/active_record/persistence.rb, line 29
def create(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr, &block) }
  else
    object = new(attributes, &block)
    object.save
    object
  end
end

How to judge it succeeds or fails

The real answer is persisted?:

if user.persisted?
  # Success
else
  # Failed
end

Why didn't use user.valid? to do it? Because sometimes it is not enough when there are some callbacks which operate other models failed:

class One < ActiveRecord::Base
  has_many :twos
  after_create :create_twos_after_create
  def create_twos_after_create
    # Use bang method in callbacks, than it will rollback while create  two failed 
    twos.create!({})    # This will fail because lack of the column `number`
  end
end

class Two < ActiveRecord::Base
  validates :number, presence: true
end

Now, we execute One.create will fail, check the log file, it will be a rollback because it failed to create two. In this case, One.create.valid? still return true, but it actually created failed, so use One.create.persisted? to replace it is necessary.

Notice: The code is tested in Rails 5.1.