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= AttributeFu
Creating multi-model forms is amazingly easy with AttributeFu.
= Get It!
$ piston import http://svn.jamesgolick.com/attribute_fu/tags/stable vendor/plugins/attribute_fu
= 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)
<i>Note: This is only relevant if using the add_associated_link method.</i>
= 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}[link:http://groups.google.com/group/attribute_fu]
Updates will be available {here}[http://jamesgolick.com/attribute_fu]
== Credits
attribute_fu was created, and is maintained by {James Golick}[http://jamesgolick.com].
Copyright (c) 2007 James Golick, GiraffeSoft Inc., released under the MIT license
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