Static Model

This is a compilation of some boilerplate code for a non–database-backed model based on ActiveModel. You might want to use this kind of static model for anything that needs to be validated but doesn’t persist to the database—such as a login authenticator or an account password reset initiator. It includes the appropriate ActiveModel modules, has a constructor that initializes attributes from a hash, and has some helper methods useful for implementing custom validations.

Full documentation is at RubyDoc.info.

Example

A user lookup class like the one below could be used as the parent class for a login authenticator or an account password reset initiator. It needs to find a user via their email, which entails validating the presence of the email attribute and providing access to the user that’s consequently looked up.

class UserLookup < StaticModel
  # An accessor to allow specifying the email to look up.
  attr_accessor(:email)

  # A reader to allow access to the user that's looked up.
  attr_reader(:user)

  # Require the email attribute.
  validates(:email,
            :presence => {:message => 'Email is required.'})

  # If the email is present, ensure that a user is associated with it.
  validate do
    no_other_errors? && user_exists?
  end

  # Find the user.
  def user
    User.find_by_email(@email)
  end

  # Add an error if no user is found.
  def user_exists?
    user ? true : add_email_error_and_return_false
  end

  protected

  # Add an error.
  def add_email_error_and_return_false
    add_error_and_return_false('Email not found', :email)
  end
end

To use this class in a Rails controller, you’d do something like

class UserLookupController < ApplicationController
  def find
    create_user_lookup
    do_something if email_valid?
  end

  protected

  def create_user_lookup
    @user_lookup = UserLookup.new(params[:user_lookup])
  end

  def do_something
    @user_lookup.user.do_something
  end

  def email_valid?
    request.post? && @user_lookup.valid?
  end
end

Testing

There is an RSpec shared example group named StaticModel that you can use to test your subclasses to ensure they contain all the necessary behavior. To make it available simply paste

require('spec/static_model')

into spec/spec_helper.rb. Then in your subclass’s spec simply use

it_should_behave_like('StaticModel')

Static Model

Example

Testing

Colophon

See also

Tested with

Contributing

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