Rails - Mar 2011 - render :collection calling partial with phantom object?

I have two models with a straightforward has_many / belongs_to
relationship:

class Premise < ActiveRecord::Base
  has_many :metered_services, :dependent => :destroy
  ...
end

class MeteredService < ActiveRecord::Base
  belongs_to :premise
  ...
end

and nested routes to match:

Demo::Application.routes.draw do
  devise_for :users
  resources :premises do
    resources :metered_services
  end
  ...
end

I want to show/edit the metered services on the same page as premise
edit page, so my views/premises/edit.html.erb file has this line:

<% Rails.logger.debug("== #{@premise.address} has
#{@premise.metered_services.count} metered services") %>
<%= render :partial => "metered_services/metered_service",
:collection
=> @premise.metered_services %>

and my stubbed views/metered_services/_metered_service.html.erb is just
this:

<% Rails.logger.debug("== _metered_service: metered_service
#{metered_service.inspect}") %>

So here''s what''s weird: With a newly created premise -- before
I''ve
added any metered services -- the _metered_service.html.erb partial gets
called with a metered service object whose ID is nil and whose
premise_id field is filled in with the owning premise.  But there should
be ZERO metered services, not one.  The console will show something
like:

== 1800 Pennsylvania Avenue has 0 metered services
  MeteredService Load (0.2ms)  SELECT "metered_services".* FROM
"metered_services" WHERE ("metered_services".premise_id =
48)
== metered_service = #<MeteredService id: nil, premise_id: 48, ... >

Is this a special "feature" of render ... :collection?  I can always
filter out metered_services with nil ids in the partial, but that seems
really odd.  Am I doing something wrong?

- ff

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maybe you have to add nested_attributes


On Mon, Feb 28, 2011 at 6:54 PM, Fearless Fool
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> I have two models with a straightforward has_many / belongs_to
> relationship:
>
> class Premise < ActiveRecord::Base
>  has_many :metered_services, :dependent => :destroy
>  ...
> end
>
> class MeteredService < ActiveRecord::Base
>  belongs_to :premise
>  ...
> end
>
> and nested routes to match:
>
> Demo::Application.routes.draw do
>  devise_for :users
>  resources :premises do
>    resources :metered_services
>  end
>  ...
> end
>
> I want to show/edit the metered services on the same page as premise
> edit page, so my views/premises/edit.html.erb file has this line:
>
> <% Rails.logger.debug("== #{@premise.address} has
> #{@premise.metered_services.count} metered services") %>
> <%= render :partial => "metered_services/metered_service",
:collection
> => @premise.metered_services %>
>
> and my stubbed views/metered_services/_metered_service.html.erb is just
> this:
>
> <% Rails.logger.debug("== _metered_service: metered_service >
#{metered_service.inspect}") %>
>
> So here''s what''s weird: With a newly created premise --
before I''ve
> added any metered services -- the _metered_service.html.erb partial gets
> called with a metered service object whose ID is nil and whose
> premise_id field is filled in with the owning premise.  But there should
> be ZERO metered services, not one.  The console will show something
> like:
>
> == 1800 Pennsylvania Avenue has 0 metered services
>  MeteredService Load (0.2ms)  SELECT "metered_services".* FROM
> "metered_services" WHERE ("metered_services".premise_id
= 48)
> == metered_service = #<MeteredService id: nil, premise_id: 48, ... >
>
> Is this a special "feature" of render ... :collection?  I can
always
> filter out metered_services with nil ids in the partial, but that seems
> really odd.  Am I doing something wrong?
>
> - ff
>
> --
> Posted via http://www.ruby-forum.com/.
>
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On Mar 1, 12:54 am, Fearless Fool
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
>
> I want to show/edit the metered services on the same page as premise
> edit page, so my views/premises/edit.html.erb file has this line:
>
> <% Rails.logger.debug("== #...@premise.address} has
> #...@premise.metered_services.count} metered services") %>
> <%= render :partial => "metered_services/metered_service",
:collection
> => @premise.metered_services %>
>
> and my stubbed views/metered_services/_metered_service.html.erb is just
> this:
>
> <% Rails.logger.debug("== _metered_service: metered_service >
#{metered_service.inspect}") %>
>
> So here''s what''s weird: With a newly created premise --
before I''ve
> added any metered services -- the _metered_service.html.erb partial gets
> called with a metered service object whose ID is nil and whose
> premise_id field is filled in with the owning premise.  But there should
> be ZERO metered services, not one.  The console will show something
> like:
>
> == 1800 Pennsylvania Avenue has 0 metered services
>   MeteredService Load (0.2ms)  SELECT "metered_services".* FROM
> "metered_services" WHERE ("metered_services".premise_id
= 48)
> == metered_service = #<MeteredService id: nil, premise_id: 48, ... >
>
> Is this a special "feature" of render ... :collection?  I can
always
> filter out metered_services with nil ids in the partial, but that seems
> really odd.  Am I doing something wrong?
>
That sounds like you''ve got an unsaved metered_service somewhere (eg
by doing premise.metered_services.build)

Fred
> - ff
>
> --
> Posted viahttp://www.ruby-forum.com/.
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Frederick Cheung wrote in post #984616:
> That sounds like you''ve got an unsaved metered_service somewhere
(eg
> by doing premise.metered_services.build)
> Fred
Yep, that''s true.  I based my code on the canonical blog posts / 
comments example, so in views/premises/edit.html.erb, I wrote:

<%= form_for([@premise,
@premise.metered_services.build(:account_identifier => "gas")]) do
|f|
%>
  <%= f.submit "add gas account" %>
<% end %>

... and it clearly calls build() whenever it renders the page.  But this
leads to two questions:

* (Curiosity:) How did render(... :collection) know about the newly
created metered_service without an ID?  I know that
premise.metered_services.build will create a new record, but it appears
that the new record doesn''t appear on the premises.metered_services
list
until it''s saved.

* (Necessity:) Assume the user is looking at
views/premises/edit.html.erb.  I want a button that says "add
metered_service to the current premise".  What''s the right way to
do
that?  (Clearly, I haven''t made friends with form_for() just yet.)

TIA.

- ff

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actually i have done somethign similiar these is my code

<%= @todo.todostags.build %>
<%= form_for(@todo) do |f| %>
  <div class="actions">
    <%= f.submit %>
  </div>
here the todo model
class Todo < ActiveRecord::Base
  has_many :todostags, :foreign_key =>"todos_id" , :primary_key
=>''id''
   accepts_nested_attributes_for :todostags, :allow_destroy => :true,
        :reject_if => proc { |attrs| attrs.all? {|k,v| v.blank?}}
end

class Todostag < ActiveRecord::Base

  belongs_to :tag ,  :foreign_key =>"tags_id"
  belongs_to :todo , :foreign_key =>"todos_id"

end


On Tue, Mar 1, 2011 at 10:49 AM, Fearless Fool
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Frederick Cheung wrote in post #984616:
>> That sounds like you''ve got an unsaved metered_service
somewhere (eg
>> by doing premise.metered_services.build)
>> Fred
>
> Yep, that''s true.  I based my code on the canonical blog posts /
> comments example, so in views/premises/edit.html.erb, I wrote:
>
> <%= form_for([@premise,
> @premise.metered_services.build(:account_identifier =>
"gas")]) do |f|
> %>
>  <%= f.submit "add gas account" %>
> <% end %>
>
> ... and it clearly calls build() whenever it renders the page.  But this
> leads to two questions:
>
> * (Curiosity:) How did render(... :collection) know about the newly
> created metered_service without an ID?  I know that
> premise.metered_services.build will create a new record, but it appears
> that the new record doesn''t appear on the
premises.metered_services list
> until it''s saved.
>
> * (Necessity:) Assume the user is looking at
> views/premises/edit.html.erb.  I want a button that says "add
> metered_service to the current premise".  What''s the right
way to do
> that?  (Clearly, I haven''t made friends with form_for() just yet.)
>
> TIA.
>
> - ff
>
> --
> Posted via http://www.ruby-forum.com/.
>
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On Mar 1, 4:49 pm, Fearless Fool
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>
> * (Curiosity:) How did render(... :collection) know about the newly
> created metered_service without an ID?  I know that
> premise.metered_services.build will create a new record, but it appears
> that the new record doesn''t appear on the
premises.metered_services list
> until it''s saved.
build adds the record to the in memory collection
>
> * (Necessity:) Assume the user is looking at
> views/premises/edit.html.erb.  I want a button that says "add
> metered_service to the current premise".  What''s the right
way to do
> that?  (Clearly, I haven''t made friends with form_for() just yet.)
>
There''s a railscast covering one possible approach:
http://railscasts.com/episodes/197-nested-model-form-part-2

Fred
> TIA.
>
> - ff
>
> --
> Posted viahttp://www.ruby-forum.com/.
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Frederick Cheung wrote in post #984876:
> There''s a railscast covering one possible approach:
> http://railscasts.com/episodes/197-nested-model-form-part-2
@Lorenzo:  Looks good.  Thanks.

@Frederick: I''m beginning to believe that "if you can imagine it,
Ryan
Bates has already coded it."  Thanks for the pointer.  I should start 
watching the railscasts regularly.

- ff

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