Rails - Apr 2006 - Help With Dependent Drop-Down and @Params

Hello All:

I am trying to create a select box that is filled with options based on 
the user''s selection in a related drop-down. I have had success with 
this before using the examples provided by the following two sources:

One posted by Rory at Rory on Rails - http://www.roryhansen.ca/?p=9

the other posted by Adam at 
http://www.adamhegedus.com/articles/2006/01/19/ajaxed-select-boxes-in-rails

Here is my problem:
The user selects a Utility and a select with Receiving Points is updated 
with the items related to the specific utility. Here is my code...

<<controller>>
  def fill_rec_points
    @lookups = Lookup.find_all_by_list_prompt(@params[:utility], :order 
=> ''list_item'')
    render :partial => ''rec_points''
    #I use a partial here to fill the span so as not to mix View and 
Business logic in the controller...
  end

<<view>>
    <p><label
for="deal_utility">Utility</label><br/>
    <%= select ''deal'', ''utility'', %w{
PG&E SoCal SDG&E Southwest},
:include_blank => true %></p>

    <span id="rec_point_list">
      <label for="deal_rec_point">Receipt
Point</label><br/>
      <select id="deal[rec_point]"
name="deal[rec_point]"></select>
    </span>

<%= observe_field("deal[utility]",
  :frequency => 0.25,
  :update => "rec_point_list",
  :url => {:action => :fill_rec_points},
  :with => "''list_item=''+value") %>

The problem seems to be that the controller is not picking anything up 
from the @params[:utility] reference. I have tried every variation of 
this I know (i.e. @params[''deal''][''utility],
@params["utility"], etc.);
all to no avail.

I know everything is set up right with the prototype.js stuff because 
when I manually enter the utility string in the controller (i.e. 
''SoCal'') instead of @params[:utility] (or whatever else I have
tried),
it works great. I just can''t seem to get the user''s selection
to pass to
my method. Any ideas?

One last thought...when I have gotten this to work before in other 
projects I have passed an id integer and not a string like I am trying 
to do now, so maybe I am referencing my @params wrong? Thanks to All and 
sorry for a long post...

-- 
Posted via http://www.ruby-forum.com/.

Hi David,

My first shot would be to try it with ''params'' instead of
''@params''.  The
''@'' is being deprecated.

Let us know if that helps.

Bill
----- Original Message -----
From: "David Hughes" <divotdave@mac.com>
To: <rails@lists.rubyonrails.org>
Sent: 2006-04-09 9:33 AM
Subject: [Rails] Help With Dependent Drop-Down and @Params

> Hello All:
>
> I am trying to create a select box that is filled with options based on
> the user''s selection in a related drop-down. I have had success
with
> this before using the examples provided by the following two sources:
>
> One posted by Rory at Rory on Rails - http://www.roryhansen.ca/?p=9
>
> the other posted by Adam at
>
http://www.adamhegedus.com/articles/2006/01/19/ajaxed-select-boxes-in-rails
>
> Here is my problem:
> The user selects a Utility and a select with Receiving Points is updated
> with the items related to the specific utility. Here is my code...
>
> <<controller>>
>   def fill_rec_points
>     @lookups = Lookup.find_all_by_list_prompt(@params[:utility], :order
> => ''list_item'')
>     render :partial => ''rec_points''
>     #I use a partial here to fill the span so as not to mix View and
> Business logic in the controller...
>   end
>
> <<view>>
>     <p><label
for="deal_utility">Utility</label><br/>
>     <%= select ''deal'', ''utility'',
%w{ PG&E SoCal SDG&E Southwest},
> :include_blank => true %></p>
>
>     <span id="rec_point_list">
>       <label for="deal_rec_point">Receipt
Point</label><br/>
>       <select id="deal[rec_point]"
name="deal[rec_point]"></select>
>     </span>
>
> <%= observe_field("deal[utility]",
>   :frequency => 0.25,
>   :update => "rec_point_list",
>   :url => {:action => :fill_rec_points},
>   :with => "''list_item=''+value") %>
>
> The problem seems to be that the controller is not picking anything up
> from the @params[:utility] reference. I have tried every variation of
> this I know (i.e. @params[''deal''][''utility],
@params["utility"], etc.);
> all to no avail.
>
> I know everything is set up right with the prototype.js stuff because
> when I manually enter the utility string in the controller (i.e.
> ''SoCal'') instead of @params[:utility] (or whatever else I
have tried),
> it works great. I just can''t seem to get the user''s
selection to pass to
> my method. Any ideas?
>
> One last thought...when I have gotten this to work before in other
> projects I have passed an id integer and not a string like I am trying
> to do now, so maybe I am referencing my @params wrong? Thanks to All and
> sorry for a long post...
>
> --
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

Bill Walton wrote:
> Hi David,
> 
> My first shot would be to try it with ''params'' instead of
''@params''.
> The
> ''@'' is being deprecated.
> 
> Let us know if that helps.
> 
> Bill
>>
Thanks Bill...I have tried that variation as well...same result. For 
some reason, I have trouble referencing form fields with the following 
name or id setting: model[object], which the <% select %> outputs in the 
html (in my case it outputs deal[utility]. I have read documentation on 
using params and @params which refers to the field via @params[:utility] 
or @params["utiliy"].

I have had this working passing an id integer but am stuck trying it 
with a string...any other ideas? Thanks...

-- 
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@params["deal"]["utility"] maybe?  I do the same thing with
a select but
don''t have my code handy right now.

David Hughes wrote:
> Thanks Bill...I have tried that variation as well...same result. For 
> some reason, I have trouble referencing form fields with the following 
> name or id setting: model[object], which the <% select %> outputs in
the
> html (in my case it outputs deal[utility]. I have read documentation on 
> using params and @params which refers to the field via @params[:utility] 
> or @params["utiliy"].
> 
> I have had this working passing an id integer but am stuck trying it 
> with a string...any other ideas? Thanks...

-- 
Posted via http://www.ruby-forum.com/.

The Barge wrote:
> @params["deal"]["utility"] maybe?  I do the same thing
with a select but
> don''t have my code handy right now.
> 
Barge...tried that to...nada. Thanks for the suggestion. It is weird.

If you could get a copy of your code to post? Maybe looking at the whole 
thing would help...


-- 
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> The Barge wrote:
>> @params["deal"]["utility"] maybe?  I do the same
thing with a select but
>> don''t have my code handy right now.
>> 
> 
> Barge...tried that to...nada. Thanks for the suggestion. It is weird.
> 
> If you could get a copy of your code to post? Maybe looking at the whole 
> thing would help...
Also...when I try @params["deal"]["utility"] I get an error
for an
undefined method. Can''t evaluate nil.[]...???

-- 
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David Hughes
>
> Also...when I try @params["deal"]["utility"] I get an
error for an
> undefined method. Can''t evaluate nil.[]...???
In looking back at the controller code you posted, I don''t see that
you''re
passing the "deal" in.  That seems to be the first problem this error
message is getting you to look for.  It may be that you just haven''t
included that piece of code.

Best regards,
Bill

OK. This is a case where you need to have a view for this controller,  
and in the view you place:

<pre><%= params.debug %></pre>

That will show you the makeup of the params object, so that you can  
figure out how you need to reference the object in the hash.

If the HTML being produced shows a form field with name="deal 
[utility]", that tells Rails to create a :deal hash, within the  
params hash, with one entry using :utility as it''s key. Referencing  
params[:deal][:utility] should return the value of that entry...

-Brian


On Apr 9, 2006, at 11:54 AM, David Hughes wrote:
> The Barge wrote:
>> @params["deal"]["utility"] maybe?  I do the same
thing with a
>> select but
>> don''t have my code handy right now.
>>
>
> Barge...tried that to...nada. Thanks for the suggestion. It is weird.

Brian Hughes ''89 wrote:
> OK. This is a case where you need to have a view for this controller,
> and in the view you place:
> 
> <pre><%= params.debug %></pre>
> 
> That will show you the makeup of the params object, so that you can
> figure out how you need to reference the object in the hash.
> 
> If the HTML being produced shows a form field with name="deal
> [utility]", that tells Rails to create a :deal hash, within the
> params hash, with one entry using :utility as it''s key.
Referencing
> params[:deal][:utility] should return the value of that entry...
> 
> -Brian
Thanks to everyone for helping so far...Brian, when I tried your 
suggestion of params[:deal][:utility] this is the error I get:

NoMethodError in Deals#fill_rec_points
You have a nil object when you didn''t expect it!
You might have expected an instance of Array.
The error occured while evaluating nil.[]
RAILS_ROOT: ./script/../config/..

Application Trace | Framework Trace | Full Trace
#{RAILS_ROOT}/app/controllers/deals_controller.rb:27:in 
`fill_rec_points''

Request
Parameters: {"list_item"=>"SoCal"}
---
Response
Headers: {"cookie"=>[],
"Cache-Control"=>"no-cache"}

Any interpretation???

Thanks Again!!!



-- 
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On Apr 9, 2006, at 12:37 PM, David Hughes wrote:
> Thanks to everyone for helping so far...Brian, when I tried your
> suggestion of params[:deal][:utility] this is the error I get:
>
> NoMethodError in Deals#fill_rec_points
> You have a nil object when you didn''t expect it!
> You might have expected an instance of Array.
> The error occured while evaluating nil.[]
>
> Request
> Parameters: {"list_item"=>"SoCal"}
Right here is where we see what your problem is. For whatever reason,  
and I''m not sure what that reason is, since I haven''t seen
your code,
the params object that your controller is getting, doesn''t have a  
"deal" object... Without a "deal" object, requesting
params[:deal] or
params["deal"] will return a nil object. This is how Ruby handles  
hash item access.

So, if you then try to reference params[:deal][:utility], you are  
asking Ruby to return the [:utility] item from a nil object, which it  
can''t do, so it throws an error. The last line of the error message,  
before the Parameters list, tells you that you are trying to do  
something with a nil object. That''s the other big clue in this error.

To "fix" this problem, you need to figure out why your form
isn''t
properly submitting data to your controller when you hit the Submit  
button. You are clicking on a submit button, aren''t you?

-Brian

> To "fix" this problem, you need to figure out why your form
isn''t
> properly submitting data to your controller when you hit the Submit
> button. You are clicking on a submit button, aren''t you?
> 
> -Brian
Thanks for the help Brian (had to leave for a bit). Actually I am trying 
to grab this data while the user is entering information on a new record 
form, PRIOR to hitting submit. Like I said before, I have had this work 
in other Rails apps. This  select control is located on the _form 
partial which is embedded in the new.rhtml view of the 
deals_controller.rb.

Could it be that it is not sending the deal hash because the record 
hasn''t been ''saved'' yet. However, the
''new'' method in the controller
calls for Deal.new, so shouldn''t it have a hash already generated for 
the deal object, with the utility item?

My code is in the first post of this thread...tell me if you need more. 
Thanks...David.


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On Apr 9, 2006, at 04:51 PM, David Hughes wrote:
> My code is in the first post of this thread...tell me if you need  
> more.
> Thanks...David.
Actually, I hadn''t read the code very closely the first time, since I  
was only trying to answer the question of the proper way to refer to  
things inside the params hash object.

However, now that I''ve taken a look at your original post code, the  
answer jumped out at me. You define your observer as:
> <%= observe_field("deal[utility]",
>   :frequency => 0.25,
>   :update => "rec_point_list",
>   :url => {:action => :fill_rec_points},
>   :with => "''list_item=''+value") %>
That :with tells the JavaScript how to send the value to your  
fill_rec_points method. You are sending the value through as  
"list_item", which is fine, but you''re not asking for
"list_item" out
of the params hash. In fact, the error you posted showed us exactly  
that:
> Application Trace | Framework Trace | Full Trace
> #{RAILS_ROOT}/app/controllers/deals_controller.rb:27:in
> `fill_rec_points''
>
> Request
> Parameters: {"list_item"=>"SoCal"}
But, since I hadn''t looked at your original code that didn''t
click
for me when I first saw it. So, you can either reference params 
[:list_item] (or params["list_item"] if you prefer), or you can  
modify your observe_field :with to be ":with =>
"''deal[utility]
=''+value", so that you''re current method of referencing
params will
work...

-Brian
Application Trace | Framework Trace | Full Trace
#{RAILS_ROOT}/app/controllers/deals_controller.rb:27:in
`fill_rec_points''

Request
Parameters: {"list_item"=>"SoCal"}

> But, since I hadn''t looked at your original code that
didn''t click
> for me when I first saw it. So, you can either reference params
> [:list_item] (or params["list_item"] if you prefer), or you can
> modify your observe_field :with to be ":with =>
"''deal[utility]
> =''+value", so that you''re current method of
referencing params will
> work...
> 
> -Brian
HALLELUJAH! It worked like a charm...I knew if someone looked at it they 
would see something I had overlooked, after pouring over it a hundred 
times.

Brian, I knew you had a good last name for a reason! Sweet!!!!!

Thanks dude, you rock...and thank you to everyone else who contributed 
to this thread. Taking time to help others is what OpenSource and Web 
2.0 is all about...what a great time to be alive!

Happy Railing!
David

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