Rails 5 Attributes API

attribute-api-example.rb

class User < ApplicationRecord
  # rails 4 way of defining virtual attribute
  attr_accessor :full_name
  
  # new rails 5 way of defining virtual attributes with datatype and default values
  attribute :name, :string, default: -> {  "No Name" }
  attribute :age, :float, default: 99

  before_save :assign_name
  before_save :assign_full_name
   
  def assign_name
    self.name = "#{first_name} #{last_name}"
  end
  def assign_full_name
    self.full_name = "#{first_name} #{last_name}"
  end
end

In rails console: 
irb:> User.new
=> #<User id: nil, first_name: nil, last_name: nil, age: "99", created_at: nil, updated_at: nil, name: "No Name">
irb:> u = User.new(first_name: "Harry", last_name: "Potter")
irb:> u.save
irb:> u
=> #<User id: 1, first_name: "Harry", last_name: "Potter", age: 99.0, created_at: "2017-03-29 16:30:16", updated_at: "2017-03-29 16:30:16", name: "Harry Potter">