poor man's reform

application_form.rb

class ApplicationForm
  include ActiveAttr::Model

  attr_reader :model

  delegate :new_record?, :persisted?, :model_name, :id, to: :model

  class << self
    # Don't sync virtual attributes to model
    # ex: attribute :accept_tos, virtual: true
    def virtual_attribute_names
      attributes.select do |name, attribute|
        attribute[:virtual]
      end.keys
    end

    def model_attribute_names
      attribute_names - virtual_attribute_names
    end
  end

  def initialize(model)
    raise ArgumentError, "model can't be blank" if model.blank?
    @model = model

    prepopulate
  end

  def validate(params)
    params.each do |name, value|
      send "#{name}=", value if self.class.attribute_names.include?(name.to_s)
    end

    valid?
  end

  def save_model
    model.save
  end

  def save
    sync_model
    save_model
  end

  private

  def prepopulate
    self.class.model_attribute_names.each do |name|
      send "#{name}=", model.send(name)
    end
  end

  def sync_model
    self.class.model_attribute_names.each do |name|
      model.send "#{name}=", send(name)
    end
  end
end

user_ban.rb

class UserBan < ApplicationRecord
  belongs_to :user
end

user_ban_form.rb

class UserBanForm < ApplicationForm
  attribute :reason
  attribute :confirm, type: Boolean, virtual: true

  validate :reason, presence: true
  
  def save_model
    model.save!
    UserMailer.banned(model.user).deliver_later
  end
end

user_bans_controller.rb

class UserBansController < ApplicationController
  def create
    @form = UserBanForm.new(current_user.ban || current_user.build_ban)
    if @form.validate(params.permit(:user_ban))
      @form.save
      redirect_back notice: "Horray!"
    else
      render "new"
    end
  end
end

user_form.rb

class UserForm < ApplicationForm
  attribute :name
  attribute :accept_tos, virtual: true
  
  validates :name, presence: true
  validates :accept_tos, acceptance: true
  
  def save_model
    model.save do
      UserMailer.welcome.deliver_later
    end
  end
end