Refactor mass assigning from a hash

Question

Here is the piece of my controller action that takes a session[:auth] hash and then assigns the values to the ActiveRecord object represented by @user whilst the key names happen to be the same.

def new
 @user = User.new
 if session[:auth].present?
 @user.first_name = session[:auth].extra.raw_info.first_name
 @user.last_name = session[:auth].extra.raw_info.last_name
 @user.username = session[:auth].extra.raw_info.username
 @user.email = session[:auth].extra.raw_info.email
 end
end

I wonder if there's a way to eliminate the duplications in assigning the values from the hash to the object.

Answer 1

This should do

def new
 attrs = %w(first_name last_name username email).map do |param|
 [param, session[:auth].extra.raw_info.send(param)]
 end
 @user = User.new Hash[attrs]
end

Answer 2

To add something to Flambino's answer, I'd suggest moving any non-trivial code to the model (code is then easier to test, re-usable and controllers are kept simple):

class User
 def self.new_from_auth(auth)
 attributes = [:first_name, :last_name, :username, :email]
 user_attributes = if auth 
 info = auth.extra.raw_info
 Hash[attributes.map { |attr| [attr, info.send(attr)] }]
 else
 {}
 end
 User.new(user_attributes)
 end
end 
class UsersController
 def new
 @user = User.new_from_auth(session[:auth])
 end
end