How to pass non-column argument to ActiveRecord new?

Question

Let's assume I have a MySQL table like below.

create table users (
    id int,
    full_name varchar(30)
);

and I want to create a model with User.new(id: 1, first_name: "Michael", last_name: "Jackson") but ActiveRecord raises unknown attribute 'first_name' for User..

Userclass is Just an example, I want it to be an meta class(like Employee < User). So, creating build method is not the way really I want.

class User
  attr_accessor :first_name, :last_name
  
  before_create :create_full_name

  def create_full_name
    self.full_name = "#{first_name} #{last_name}"
  end
end 

user = User(id: 1)
user.first_name = "Michael"
user.last_name = "Jackson"

Is pretty close, but this needs an additional assignment from outside. I don't want this redundancy.

Is there any way to this?

Answer 1

You can use the initialize method to set the attributes. You can also use the send method to set the attributes. For example:

class User
  attr_accessor :first_name, :last_name

  def initialize(attributes = {})
    attributes.each do |name, value|
      send("#{name}=", value)
    end
  end
end

user = User.new(id: 1, first_name: "Michael", last_name: "Jackson")
p user.first_name
p user.last_name

# Output:
# "Michael"
# "Jackson"