Form Objects - Refactoring Rails the Clean Way

base_form.rb

class BaseForm
  include ActiveModel::Model
  include ActiveModel::Validations

  def initialize(params={})
    super(params)
  end
end

profile_form.rb

class ProfileForm
  # Make ProfileForm acts like a model
  include ActiveModel::Model
  include ActiveModel::Validations
  
  attr_accessor :user, :profile
  
  # This is shorthand for
  #   def user_attributes=(attribute)
  #     user.attributes = attributes
  #   end
  # 
  # When calling super in initialize, this auto assigns
  # params[:user_attributes] to self.user
  # Thus, you are able to use the same nested form syntax in your views
  # https://guides.rubyonrails.org/form_helpers.html#nested-forms
  delegate :attributes=, to: :user, prefix: true
  delegate :attributes=, to: :profile, prefix: true

  validate :profile_is_complete
  
 
  def initialize(user, params={})
    @params = params
    @user = user
    @profile = user.profile || new_user_profile
    
    # Calling super params utilizes ActiveModel
    # thus self assigning attributes to users
    super(params)
  end

  def save
    # early return form validation checks for errors 
    # in the form and return false to avoid the saving process
    return false unless valid?
    
    # Wrap save in a transaction
    # Use `Model#save!` with a bang to ensure an error
    # is raised to rollback thus avoiding partial save.
    ActiveRecord::Base.transaction do
      @user.save!
      @profile.save!
    end
    
    # Once saving is successful, you may perform extra steps like
    # sending emails, nofifying admins
    AdminNofitication.new(message: "A user created a new profile!").call
    UserMailer.profile_creation(@user, @profile).deliver_later
    
    # Always return true when successful to
    # notify controller to perform success action
    true
  rescue ActiveRecord::RecordInvalid
    false
  end

  private

  # Setup a new profile
  def new_user_profile
    @user.build_profile.tap do |profile|
      profile.attributes = {
        # setup default profile attributes
      }
    end
  end
  
  def profile_is_complete
    # Perform custom validation
    @profile.errors.add(:le_attribute, "You forgot to do this") if @profile.le_attributes.has_something_wrong

    # Or use context/dry-validation
    # https://guides.rubyonrails.org/active_record_validations.html#on
    @profile.valid?(:complete)
  end
end

profiles_controller.rb

class ProfilesController < ApplicationController
  def new
    @form = ProfileForm.new(current_user)
  end
  
  def create
    @form = ProfileForm.new(current_user, form_params)
    
    # Now your form can act like a model
    if @form.save
      flash[:success] = "This is successful"
      redirect_to :success
    else
      flash[:error] = "Please look into the errors"
      render :new
    end
  end
  
  private
  
  def form_params
    params.require(:profile_form).permit(
      user_attributes: [:name, :attributes_to_update],
      profile_attributes: [:country, :bio, :more_attributes_to_update]
    )
  end
end