Quack like an ActiveRecord object

active_model.rb

class FakeRecord
  # ActiveModel plumbing to make `form_for` work
  extend ActiveModel::Naming
  include ActiveModel::Conversion
  include ActiveModel::Validations

  attr_accessor :foo, :bar

  validates :foo, presence: true

  def initialize(attributes = {})
    self.foo = attributes[:foo]
  end

  def save
    return false unless valid?

    # Do something...

    true
  rescue MyError
    errors.add(:foo, "Something went wrong")
    false
  end

  def persisted?
    false
  end
end

This can be made simpler by including ActiveModel::Model which will define the constructor and #persisted? for us. https://github.com/rails/rails/blob/master/activemodel/lib/active_model/model.rb#L59-L97