default_user.rb

class DefaultUser
  attr_reader :params

  def initialize(params)
    @params = params
  end

  def create
    User.create(default_user_params)
  end

  def default_user_params
    clean_params.merge(defaults)
  end

  def clean_params
    # do some stuff to incoming params
  end

  def defaults
    {
      number: 0.0,
      address: build_address,
    }
  end

  def build_address
    # some logic to build an address
  end
end