AttributeFu¶ ↑

Creating multi-model forms is amazingly easy with AttributeFu.

Get It!¶ ↑

$ script/plugin install git://github.com/giraffesoft/attribute_fu.git

Conventions¶ ↑

attribute_fu requires the fewest keystrokes if you follow certain conventions.

• The partial that contains your associated model’s form is expected to be called _class_name.template_ext (e.g. the partial for your Task model would be called _task.html.erb)

• The DOM element that contains the form for your model should have the CSS class .class_name (e.g. the CSS class for your Task would be .task)

• The DOM element that contains all of the rendered forms should have the DOM ID #class_name (e.g. the DOM ID of the container of your Task forms would be #tasks) Note: This is only relevant if using the add_associated_link method.

Example¶ ↑

In this example, you’ll build a form for a Project model, in which a list of associated (has_many) tasks can be edited.

The first thing you need to do is enable attributes on the association.

class Project < ActiveRecord::Base
  has_many :tasks, :attributes => true
end

Instances of Project will now respond to task_attributes, whose format is as follows:

@project.task_attributes = {
  @project.tasks.first.id => {:title => "A new title for an existing task"},
  :new => {
    "0" => {:title => "A new task"}
  }
}

Any tasks that already exist in that collection, and are not included in the hash, as supplied to task_attributes, will be removed from the association when saved. Most of the time, the form helpers should take care of building that hash for you, though.

Form Helpers¶ ↑

If you follow certain conventions, rendering your associated model’s form elements is incredibly simple. The partial should have the name of the associated element’s type, and look like a regular old form partial (no messy fields_for calls, or any nonsense like that).

## _task.html.erb
<div class="task">
  <label>Title</label>
  <%= f.text_field :title %>
</div>

Then, in your parent element’s form, call the render_associated_form method on the form builder, with the collection of elements you’d like to render as the only argument.

## _form.html.erb
<%= f.render_associated_form(@project.tasks) %>

That call will render the partial named _task.html.erb with each element in the supplied collection of tasks, wrapping the partial in a form builder (fields_for) with all the necessary arguments to produce a hash that will satisfy the task_attributes method.

You may want to add a few blank tasks to the bottom of your form; no need to do that in the controller anymore.

<%= f.render_associated_form(@project.tasks, :new => 3) %>

Since this is Web2.0, no form would be complete without some DHTML add and remove buttons. Fortunately, there are some nifty helpers to create them for us. Simply calling remove_link on the form builder in your _task partial will do the trick.

## _task.html.erb
<div class="task">
  <label>Title</label>
  <%= f.text_field :title %>
  <%= f.remove_link "remove" %>
</div>

Creating the add button is equally simple. The add_associated_link helper will do all of the heavy lifting for you.

## _form.html.erb
<%= f.add_associated_link "Add New Task", @project.tasks.build %>

That’s all you have to do to create a multi-model form with attribute_fu!

Discarding Blank Child Models¶ ↑

If you want to show a bunch of blank child model forms at the bottom of your form, but you only want to save the ones that are filled out, you can use the discard_if option. It accepts either a proc:

class Project < ActiveRecord::Base
  has_many :tasks, :attributes => true, :discard_if => proc { |task| task.title.blank? }
end

…or a symbol…

class Project < ActiveRecord::Base
  has_many :tasks, :attributes => true, :discard_if => :blank?
end

class Task < ActiveRecord::Base
  def blank?
    title.blank?
  end
end

Using a symbol allows you to keep code DRYer if you are using that routine in more than one place. Both of those examples, however, would have the same effect.

Updates¶ ↑

Come join the discussion on the mailing list

Updates will be available here

Running the tests¶ ↑

To run the tests, you need Shoulda, mocha and multi-rails:

$ sudo gem install thoughtbot-shoulda --source http://gems.github.com/
$ sudo gem install mocha multi_rails

Credits¶ ↑

attribute_fu was created, and is maintained by James Golick.

Copyright © 2007 James Golick, GiraffeSoft Inc., released under the MIT license