Help with nested models and fields_for


#1

Hi folks.

I’m trying to do stuff with models nested one layer deeper than I’ve
done in the past…and it’s just not working properly. Here’s the
situation:

  • I have three models involved here: Recipe, IngredientLine, and
    Ingredient (it’s a cookbook application).

class Recipe < ActiveRecord::Base
has_many :ingredient_lines
has_many :ingredients, :through => :ingredient_lines
end

class IngredientLine < ActiveRecord::Base
belongs_to :ingredient
belongs_to :recipe
end

class Ingredient < ActiveRecord::Base
has_many :ingredient_lines
has_many :recipes, :through => :ingredient_lines
end

  • I’m trying to develop a form which edits a Recipe along with its
    associated IngredientLines and Ingredients. Right now, I’ve been
    working with this sort of thing (it’s a Facebook app, hence the .fbml
    extension, and I’m only doing relevant excerpts so as not to take up
    too much space here):

— recipe/views/new.fbml.haml —

  • form_for(@current_object) do |f|
    = f.text_field :name
    = render :partial => ‘ingredient’, :locals => {:f => f}
    = f.text_area :instructions

— recipe/views/_ingredient.fbml.haml —

  • f.fields_for :ingredient_lines, :index => nil do |ff|
    %td= ff.text_field :quantity, :size => 3, :maxlength => 3, :id =>
    nil
    %td= ff.text_field :unit, :id => nil
    • ff.fields_for :ingredient do |i|
      %td= i.text_field :name, :id => nil
  • I’ve tried this with fields_for instead of f.fields_for as well.

  • There’s some JavaScript to produce multiple copies of the partial
    for multiple ingredient, but I’m omitting that since it’s not relevant
    here.

  • The HTML/FBML output for this is as expected:

So far so good. But here’s the problem: submissions don’t work quite
properly
. When I fill out the form and submit it, I get params
entries like
“recipe”=>{“name”=>“Recipe”, “ingredient_lines”=>[{“quantity”=>“1”,
“unit”=>“cup”, “ingredient”=>{}}], “instructions”=>“Preheat oven to
350°…”}. Note that ingredient_lines[0].ingredient.name is missing,
even if I enter text in the corresponding form field – in other
words, what I should be seeing is something like “recipe”=>
{“name”=>“Recipe”, “ingredient_lines”=>[{“quantity”=>“1”,
“unit”=>“cup”, “ingredient”=>{“name” => “flour”}}],
“instructions”=>“Preheat oven to 350°…”}. What am I doing wrong?

Any suggestions would be helpful. Thanks in advance!

Best,

Marnen Laibow-Koser
removed_email_address@domain.invalid
http://www.marnen.org


#2

Marnen Laibow-Koser wrote:

words, what I should be seeing is something like “recipe”=>
{“name”=>“Recipe”, “ingredient_lines”=>[{“quantity”=>“1”,
“unit”=>“cup”, “ingredient”=>{“name” => “flour”}}],
“instructions”=>“Preheat oven to 350°…”}.

I believe this is a limitation of Rails’ parameter parsing.
It can’t handle more that one level below an array parameter.

A solution is to create an ingredient_name accessor in
IngredientLine, and arrange to have this rendered and posted.


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#3

On Dec 20, 8:22 am, Mark Reginald J. removed_email_address@domain.invalid wrote:

I believe this is a limitation of Rails’ parameter parsing.

I was afraid of that. This may be the excuse I need to start hacking
the core. :slight_smile:

It can’t handle more that one level below an array parameter.

Are you sure? I’ve seen a few examples on the Web which imply that
this should work.

By “array parameter”, do you specifically mean one with a numeric
subscript, so that object[foo][bar][baz] would work as expected,
although objects[][foo][bar][baz] would not? If so, that would
explain some – not all – of the examples I’ve seen.

A solution is to create an ingredient_name accessor in
IngredientLine, and arrange to have this rendered and posted.

Yeah, but that’s so ugly

Best,

Marnen Laibow-Koser
removed_email_address@domain.invalid
http://www.marnen.org


#4

On Dec 21, 11:42 am, Mark Reginald J. removed_email_address@domain.invalid wrote:

Marnen Laibow-Koser wrote:

It can’t handle more that one level below an array parameter.

Are you sure? I’ve seen a few examples on the Web which imply that
this should work.

I can confirm that it’s broken in Rails 2.0.2, and fixed
in Rails >= 2.1.0.

Then something else is going on. I’m using Rails 2.2.2 and having
these problems.

[…]

objects[][foo] works, but objects[][foo][bar] did not.

And still apparently does not. Any other thoughts?

Best,

Marnen Laibow-Koser
removed_email_address@domain.invalid
http://www.marnen.org


#5

Marnen Laibow-Koser wrote:

It can’t handle more that one level below an array parameter.

Are you sure? I’ve seen a few examples on the Web which imply that
this should work.

I can confirm that it’s broken in Rails 2.0.2, and fixed
in Rails >= 2.1.0.

By “array parameter”, do you specifically mean one with a numeric
subscript, so that object[foo][bar][baz] would work as expected,
although objects[][foo][bar][baz] would not? If so, that would
explain some – not all – of the examples I’ve seen.

objects[][foo] works, but objects[][foo][bar] did not.


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#6

On Dec 22, 1:22 am, Mark Reginald J. removed_email_address@domain.invalid wrote:

“recipe”=>{“ingredient_lines”=>[{“ingredient”=>{}}]}

You may like to run the same test.

Thanks for the suggestion. I tried the same test, and got interesting
if disheartening results. When I had recipe[ingredient_lines][]
[ingredient][name] as the only form field, I got the same results as
you. But the moment I added recipe[ingredient_lines][][unit],
[ingredient][name] stopped working. This was true both with Rails
2.1.2 and 2.2.2. I think I may be running into a bug in Rails.

Best,

Marnen Laibow-Koser
removed_email_address@domain.invalid
http://www.marnen.org


#7

Marnen Laibow-Koser wrote:

these problems.

[…]

objects[][foo] works, but objects[][foo][bar] did not.

And still apparently does not. Any other thoughts?

The test I did was to post from the following view.

On Rails >= 2.1 I got the correct
“recipe”=>{“ingredient_lines”=>[{“ingredient”=>{“name”=>“hhh”}}]}

on 2.0.2 I got what you’re seeing:
“recipe”=>{“ingredient_lines”=>[{“ingredient”=>{}}]}

You may like to run the same test.

If you see the same, perhaps the problem manifests when extra
parameters are added. You can try adding fields until you
are posting your complete form. Please post what you find out.


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#8

Mark Reginald J. wrote:

Below is a patch that seems to fix the problem. I haven’t
yet run the rails test suite on it, nor added a test that would
have broken the original.

I’ve confirmed that this patch fixes the problem without regression.

http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1622-incorrect-parsing-of-query-parameters-with-mixed-depth-nesting-inside-an-array


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#9

Marnen Laibow-Koser wrote:

Thanks for the suggestion. I tried the same test, and got interesting
if disheartening results. When I had recipe[ingredient_lines][]
[ingredient][name] as the only form field, I got the same results as
you. But the moment I added recipe[ingredient_lines][][unit],
[ingredient][name] stopped working. This was true both with Rails
2.1.2 and 2.2.2. I think I may be running into a bug in Rails.

Thanks for running that test.

Below is a patch that seems to fix the problem. I haven’t
yet run the rails test suite on it, nor added a test that would
have broken the original.

Just run the patch command in actionpack-2.2.2/lib/action_controller

— request.rb 2008-12-23 13:07:00.000000000 +1100
+++ request.rb.new 2008-12-23 14:37:30.000000000 +1100
@@ -811,9 +811,9 @@
top[-1][key] = value
else
top << {key => value}.with_indifferent_access

  •          push top.last
    
  •          value = top[key]
            end
    
  •        push top.last
    
  •        value = top[key]
          else
            top << value
          end
    


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#10

On Dec 23, 1:13 pm, Mark Reginald J. removed_email_address@domain.invalid wrote:

Mark Reginald J. wrote:

Below is a patch that seems to fix the problem. I haven’t
yet run the rails test suite on it, nor added a test that would
have broken the original.

I’ve confirmed that this patch fixes the problem without regression.

Hey, this is quite a Christmas present – thanks very much! I was
about to start poking around in the core to fix this, but you beat me
to it. (The patch you posted here didn’t actually work, but the one
on the Lighthouse ticket did.) And it solves the problem beautifully.

http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/1622-incorrect-parsing-of-query-parameters-with-mixed-depth-nesting-inside-an-array

I had already created a ticket for this, which Fred closed as a
duplicate before I could do so. So we’re cool. Thanks again.

Best,

Marnen Laibow-Koser
removed_email_address@domain.invalid
http://www.marnen.org