Informal

Informal is a small gem that enhances a Plain Old Ruby Object so it can be used with Rails 3 form helpers in place of an ActiveRecord model. It works with the Rails form_for helper, and simple_form as well.

Here's a quick (and slightly insane) example:

# models/command.rb
require "informal"
class Command
  include Informal::Model
  attr_accessor :command, :args
  validates_presence_of :command
  def run; `#{command} #{args}`; end
end

# views/commands/new.html.erb
<%= form_for @command do |form| %>
  <%= form.text_field :command %>
  <%= form.text_field :args %>
  <%= form.submit "Do It!" %>
<% end %>

# controllers/commands_controller.rb
def create
  command = Command.new(params[:command])
  if command.valid?
    command.run
  end
end

Installation

It's a Ruby gem, so just install it with gem install informal, add it to your bundler Gemfile, or do whatever you like to do with gems. There is nothing to configure.

Usage

The insanity of the above example aside, Informal is pretty useful for creating simple RESTful resources that don't map directly to ActiveRecord models. It evolved from handling login credentials to creating model objects that were stored in a serialized attribute of a parent resource.

In many ways using an informal model is just like using an AR model in controllers and views. The biggest difference is that you don't save an informal object, but you can add validations and check if it's valid?. If there are any validation errors, the object will have all the usual error decorations so that error messages will display properly in the form view.

Initialization, #super and attributes

If you include Informal::Model, your class automatically gets an #initialize method that takes a params hash and calls setters for all attributes in the hash. If your model class inherits from a class that has its own #initialize method that needs to get the super call, you should instead include Informal::ModelNoInit, which does not create an #initialize method. Make your own #initialize method, and in that you can assign the attributes using the #attributes= method and also call super with whatever args are needed.

Overriding the `model_name`

If you name your model InformalCommand, form params get passed to your controller in the params[:informal_command] hash. As that's a bit ugly and perhaps doesn't play well with standing in for a real ActiveRecord model, Informal provides a method to override the model name.

class InformalCommand
  informal_model_name "Command"
  # ...
end

Note: the informal_model_name feature is available only in Rails 3.1 or greater (unless somebody back-ports the required API change to 3.0.x).

Idiosyncrasies

The standard way that Rails generates ids for new records is to name them like command_new, as opposed to command_17 for persisted records. I've found that when using informal models I often want more than one per page, and it's helpful to have a unique id for JavaScript to use. Therefore Informal uses the model's object_id to get a unique id for the record. Those ids in the DOM will look like command_2157193640, which would be scary if you did anything with those memory addresses except use them for attaching scripts.