Rails - Apr 2009 - Complex forms: only one level of “arrayness” is allowed?

Hi all,

I thought I was trying to do something rather simple, but it has
caused me a lot of headaches. Here it is:

- in my program: model_a has_many model_b. model_b has_many model_c.

- in the user interface, I would like the user to be able to fill the
information for one model_a, one or more associated model_bs
(corresponding fields could be added with a set of links ''add/remove a
model_b''), and for each model_b added, one or more model_c (with the
same mechanism).

Thanks to the great tutorial "Handle multiple models in one form",
it''s easy to handle the first step (any number of model_b per
model_a), but I can''t get the second step to work. The natural
indexing should (I think) be:

"model_a[model_b_attributes][][model_c_attributes][][an_attribute]"

But it doesn''t seem to work. I read here
http://guides.rubyonrails.org/form_helpers.html
that "only one level of “arrayness” is allowed" and that I should use
hashes instead, but I am not quite sure I understand how to do it.

Do you have any idea?

Thanks a lot
PJ

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On Apr 15, 1:07 am, PJ
<camillieri...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
"model_a[model_b_attributes][][model_c_attributes][][an_attribute]"
>
> But it doesn''t seem to work. I read
herehttp://guides.rubyonrails.org/form_helpers.html
> that "only one level of “arrayness” is allowed" and that I should
use
> hashes instead, but I am not quite sure I understand how to do it.
>
> Do you have any idea?
What that comment is saying is that you can replace an array eg
[a,b,c] with a hash eg {1 => a, 2=> b, 3=>c}
Generating those keys is up to your client side code, approaches
included using a number you increment or going for some unique thing
you generate on the spot (eg time in milliseconds concatenated with a
random number) so that you don''t have to keep track of how many fields
and what not you have created clientside.

Fred

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Thanks Fred.

Considering there is a bit of "wizardry" that needs to be done and
that Rails doesn''t include helpers to do this simply, does it mean it
is not recommended to build such complex forms?

I am not very experienced with Rails, but I love the fact it is very
"clean" and I feel a bit cautious having to generate keys manually.

PJ

On Apr 15, 9:05 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On Apr 15, 1:07 am, PJ
<camillieri...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
> >
"model_a[model_b_attributes][][model_c_attributes][][an_attribute]"
>
> > But it doesn''t seem to work. I read
herehttp://guides.rubyonrails.org/form_helpers.html
> > that "only one level of “arrayness” is allowed" and that I
should use
> > hashes instead, but I am not quite sure I understand how to do it.
>
> > Do you have any idea?
>
> What that comment is saying is that you can replace an array eg
> [a,b,c] with a hash eg {1 => a, 2=> b, 3=>c}
> Generating those keys is up to your client side code, approaches
> included using a number you increment or going for some unique thing
> you generate on the spot (eg time in milliseconds concatenated with a
> random number) so that you don''t have to keep track of how many
fields
> and what not you have created clientside.
>
> Fred
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On Apr 15, 5:09 pm, PJ
<camillieri...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Thanks Fred.
>
> Considering there is a bit of "wizardry" that needs to be done
and
> that Rails doesn''t include helpers to do this simply, does it mean
it
> is not recommended to build such complex forms?
>
> I am not very experienced with Rails, but I love the fact it is very
> "clean" and I feel a bit cautious having to generate keys
manually.
>
There is the nested forms stuff in rails 2.3 (unfortunately not yet
documented in the guide).

Fred
> PJ
>
> On Apr 15, 9:05 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> wrote:
>
> > On Apr 15, 1:07 am, PJ
<camillieri...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > >
"model_a[model_b_attributes][][model_c_attributes][][an_attribute]"
>
> > > But it doesn''t seem to work. I read
herehttp://guides.rubyonrails.org/form_helpers.html
> > > that "only one level of “arrayness” is allowed" and
that I should use
> > > hashes instead, but I am not quite sure I understand how to do
it.
>
> > > Do you have any idea?
>
> > What that comment is saying is that you can replace an array eg
> > [a,b,c] with a hash eg {1 => a, 2=> b, 3=>c}
> > Generating those keys is up to your client side code, approaches
> > included using a number you increment or going for some unique thing
> > you generate on the spot (eg time in milliseconds concatenated with a
> > random number) so that you don''t have to keep track of how
many fields
> > and what not you have created clientside.
>
> > Fred
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PJ wrote:
[...]
> The natural
> indexing should (I think) be:
> 
>
"model_a[model_b_attributes][][model_c_attributes][][an_attribute]"
> 
> But it doesn''t seem to work.
[...]

There is a bug in Rails at least up to 2.2.2 that you may be running 
into.  I reported it on this list around Christmas 2008.  If you search 
the archives for my name around that time, you will find the ensuing 
discussion and a patch that Fred submitted for the bug.  Good luck!

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

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