Vixiom Axioms

October 21, 2006

Use a partial form with form_for

Filed under: Ruby on Rails — Alastair @ 12:56 pm

I’m sure the cool kids know this already but it gave me a problem so I thought I’d post it.

When using “render :partial => ‘form’”, where ‘form’ is being rendered for a ‘new’ and edit ‘view’, you need to pass a local variable for your model object.

Originally I had

<% form_for :product, @product, :url => { :action => ‘update’, :id => @product.id } do |f| %>

<!–[form:product]–>
<div id=‘container‘>
    <%= render :partial => ‘form’ %>
</div>

<button type=“submit”>Save Listing</button>

and here’s the solution with ‘f’ passed as a local variable to the partial

<% form_for :product, @product, :url => { :action => ‘update’, :id => @product.id } do |f| %>

<!–[form:product]–>
<div id=‘container‘>
    <%= render :partial => ‘form’, :locals => { :f => f } %>
</div>

<button type=“submit”>Save Listing</button>
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16 Comments »

  1. I also think you can do something like render :partial => ‘form’, :object => f which is a few less characters (at least at one point I remember using that).

    Comment by John Nunemaker — October 25, 2006 @ 1:16 pm

  2. The ‘:object =>f’ syntax might be deprecated - http://api.rubyonrails.com/classes/ActionController/Base.html#M000206. The ‘:locals => { :f => f }’ thing definitely works.

    Thanks for posting this - guess I’m not cool either because I wasn’t sure how to use form_for and partials either.

    Comment by Rich — November 7, 2006 @ 10:31 am

  3. Ah, makes sense. Thanks for checking.

    Comment by John Nunemaker — November 21, 2006 @ 7:52 am

  4. Ahhh… this makes sense now! Just passing your model as a local variable into your partial. Now the question is, why form_tag’s are still being used in scaffolds!

    Comment by Justin Reagor — February 18, 2007 @ 11:38 am

  5. Thanks… I was puzzled by this also and spent a few hours trying to figure out what I was doing wrong!
    – Another Uncool Ruby Kid

    Comment by Nola Stowe — March 3, 2007 @ 8:34 pm

  6. Why not do something like:

    ‘form’, :locals => { :form_action => :create } %>

    and put the form_for tag in the partial. If you need text for the button as well, you could pass that in.

    Comment by Jun-Dai — March 30, 2007 @ 4:08 am

  7. I like Jun-Dai’s comment but the reason I think most people come across this problem is from the rails generated scaffold which produces a form_tag and people learn the magic of form_for and then render partial fails because in its local context it doesn’t know about the form. This post shows how to register the form in the local scope of the partial.

    Jun-Dai’s comment is really interesting as well because it goes along with the Rails Recipe of cleaning up the controller actions new, create, edit and update and consolidating them into 1 method.

    Comment by Wes Bailey — May 15, 2007 @ 11:37 pm

  8. Passing the actual FormBuilder instance as a local is definitely the way to go.

    Comment by Duncan Beevers — June 15, 2007 @ 6:34 pm

  9. We just applied a patch that allows you to do:

    f %>

    This will render the _form partial with a local variable called form referencing the FormBuilder.

    More info on http://elctech.com/2008/1/16/patching-rails-rendering-form-partials

    Comment by Damian Janowski — January 18, 2008 @ 8:35 am

  10. I have a simple form, it has a text_field and a text_area. I want to add
    2 submit buttons. Each one will do a different action. I was thinking I
    could do form_for, and fields_for, but then I thought that fields_for is
    used for having two objects, but I only have one. I know I could just
    make them images, and links, but I suck at photoshop, and my boss is one
    of those people that feels he is a designer, and he tells me that I have
    to have some sort of flashing animated gif that is on the right hand
    side, and some link that has to be red over on the left side. He also
    told me I have to have two buttons, but I don’t know how to do that.

    Comment by plastik — February 28, 2008 @ 5:10 am

  11. what about this solution http://www.myersds.com/notebook/2006/09/10/multiple_submit_buttons_on_a_form_with_rails

    Comment by Alastair — February 28, 2008 @ 8:34 am

  12. Excellent thanks for this tip I was trying to figure out the same thing!

    Jason

    Comment by Jason — March 25, 2008 @ 5:09 pm

  13. […] This was giving me problems. This solved it. […]

    Pingback by Scott Motte » Blog Archive » How to put a partial form in form_for — August 14, 2008 @ 3:44 pm

  14. Awesome, this is a life-saver. Thanks for the post.

    Comment by Trevor — September 8, 2008 @ 11:16 am

  15. Im completely new at this whole rails business, and while im really enjoying it im not really getting a lot. I see that this works well, but what is the :locals symbol saying?

    Comment by Jason Calleiro — November 11, 2008 @ 4:04 pm

  16. hey jason, :locals is enabling the partial ‘form’ to have access to the variable ‘f’ which is the form_for the model ‘product’

    so if the model :product has product.name and product.type etc then you can create form elements like

    f.text_field :name
    f.text_field :type

    and they will be bound to the :product model (ie if you are editing a product it’s current values will be set in the text inputs)

    Comment by Alastair — November 11, 2008 @ 10:23 pm

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