Introducing MiniForm

My last blog post - Dealing with form objects, got me thinking about form objects. I also had a 12 hours flight to San Francisco, where I was meeting my teammates at Product Hunt.

During that flight, I went back and checked all of my custom form implementations. I gathered them together in a folder and started combining and extracting the common parts. By the end of the flight I almost had what now is MiniForm. (I had to change its name several times since I'm not very good with names and most of the decent names are not available).

MiniForm allows the following code:

 class RegistrationForm  
  include ActiveModel::Model

  attr_reader :user, :account

  attr_accessor :first_name, :last_name, :email, :name, :plan, :terms_of_service

  # user validation
  validates :first_name, presence: true
  validates :last_name, presence: true
  validates :email, presence: true, email: true

  # account validation
  validates :account_name, presence: true

  # form custom validation
  validates :plan, inclusion: {in AccountPlan::VALUES}
  validates :terms_of_service, acceptance: true

  # ensure uniqueness
  validate :ensure_unique_user_email
  validate :ensure_unique_account_name

  def initialize
    @user    = User.new
    @account = Account.new owner: @user
  end

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

    if valid? & user.update(user_attributes) && account.update(account_attributes)
      account.users << user
      AccountWasCreated.perform_later(account)
    else
      false
    end
  end

  private

  def ensure_unique_user_email
    errors.add :email, 'already taken' if User.where(email: email).any?
  end

  def ensure_unique_account_name
    errors.add :name, 'already taken' if Account.where(name: name).any?
  end

  def user_attributes
    {first_name: first_name, last_name: last_name, email: email}
  end

  def account_attributes
    {plan: plan, name: name}
  end
end  

To become:

class RegistrationForm  
  include MiniForm::Model

  # `model` delegates attributes to models 
  # and copies the validations from them
  model :user, attributes: %i(first_name last_name email), save: true
  model :account, attributes: %i(name plan), save: true

  attributes :terms_of_service

  validates :plan, inclusion: {in AccountPlan::VALUES}
  validates :terms_of_service, acceptance: true

  def initialize
    @user    = User.new
    @account = Account.new owner: @user
  end

  # `update` calls `perform` if model is valid
  # and models are saved
  def perform
    account.users << user
    AccountWasCreated.perform_later(account)
  end
end