Add model virtual attribute

Before:

<% form_for @user do |f| %>
  <%= text_field_tag :full_name %>
<% end %>

class UsersController < ApplicationController

  def create
    @user = User.new(params[:user])
    @user.first_name = params([:full_name]).split(' ', 2).first
    @user.last_name = params([:full_name]).split(' ', 2).last
    @user.save
  end

end

After:

class User < ActiveRecord::Base

  def full_name
    [first_name, last_name].join(' ')
  end

  def full_name=(name)
    split = name.split(' ', 2)
    self.first_name = split.first
    self.last_name = split.last
  end

end

<% form_for @user do |f| %>
  <%= f.text_field :full_name %>
<% end %>

class UsersController < ApplicationController

  def create
    @user = User.create(params[:user])
  end

end