ActiveModel::Form

ActiveModel lets you easily create objects that can be used in form helpers and even support round-tripping (assigning the submitted params again)

But ActiveModel doesn't support out of the box argument parsing, e.g. having a datetime attribute be a datetime attribute and a boolean attribute be a boolean attribute.

This fixes that.

ActiveModel::Form happened because the "tableless model" presented in RailsCast 219 wasn't as powerful as the "real deal" from RailsCast 193.

Installation

Add this line to your application's Gemfile:

gem 'activemodel-form'

Usage

In the controller:

class FormsController < ApplicationController
  class SearchForm < ActiveModel::Form
    self.model_name = 'q' # => <input name="q[username]" ... /> etc.
    attribute :username, :string
    attribute :created_at, :date_time
    attribute :locked, :boolean

    validates_presence_of :username
    validates_presence_of :created_at
  end
  
  def search
    @search = SearchForm.new(params[:q])
    if @search.valid?
      @users = User.where(username: @search.username) # ...
    end
  end
end

and the view:

<%= form_for @search, url: form_path do |f| %>
  <%= f.text_field :username %><br />
  <%= f.datetime_select :created_at %><br />
  <%= f.check_box :locked %><br />
  <%= f.submit %>
<% end %>

If you use simple_form or formtastic, they automatically create date_time or boolean inputs based on your form object.

Also check out the example project.

Future

This gem doesn't hook into any Rails (or simple_form or formtastic) internals and doesn't monkey patch anything, it only uses the ActiveModel API. So it should be future proof.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request