Rails - Feb 2006 - how to add multiple new records from one form

I''m trying to provide our customers with a page where they can add up
to
20 items to their cart in one form.  The form simply has 20 rows with 
each row containing a text input for product code and a text input for 
quantity.

I''ve tried having the controller create an array that has an object for
each row by looping through something like:

@new_items[1] = Cart.new

and the controller is happy with that, but the template isn''t--it gives
an error like "@new_items[1] is not allowed as an instance variable 
name".

I can get the whole thing working if I use non-model form objects in the 
template, but then I lose the Rails error magic where it highlights any 
errant fields and gives a message.

Why can I create Cart objects within an array in the controller, but not 
use them in the template.

Or am I going about this completely wrong??

Any help is appreciated greatly.

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Shawn Goble wrote:
> I''m trying to provide our customers with a page where they can add
up to
> 20 items to their cart in one form.  The form simply has 20 rows with 
> each row containing a text input for product code and a text input for 
> quantity.
> 
> I''ve tried having the controller create an array that has an
object for
> each row by looping through something like:
> 
> @new_items[1] = Cart.new
> 
> and the controller is happy with that, but the template isn''t--it
gives
> an error like "@new_items[1] is not allowed as an instance variable 
> name".
Perhaps:

<% for i in 1..20 do %>
<%= text_field  :new_items, :product_code, :index => i %>
<%= text_field  :new_items, :quantity, :index => i %>
<% end %>


case request.method
   when :get then @new_items = Array.new(20) { Cart.new }
   when :post
     all_valid = true
     @new_items = []
     params[:new_items].each_value { |p| @new_items << (c=Cart.new(p));
all_valid &&= c.valid? }
     if !@new_items.empty? && all_valid
        @user.items << @new_items
        @user.save(false)
        redirect_to :action => ''show_cart''
     else
       flash[:error] = ''No items entered'' if @new_items.empty?
       (20-@new_items.length).times { @new_items << Cart.new }
     end
end

-- 
We develop, watch us RoR, in numbers too big to ignore.

Mark Reginald James wrote:
> Shawn Goble wrote:
>> and the controller is happy with that, but the template
isn''t--it gives
>> an error like "@new_items[1] is not allowed as an instance
variable
>> name".
> 
> Perhaps:
> 
> <% for i in 1..20 do %>
> <%= text_field  :new_items, :product_code, :index => i %>
> <%= text_field  :new_items, :quantity, :index => i %>
> <% end %>
> 
Hi Mark,

My query with this is, would Rails look at the number enclosed within 
the square brackets and subsequently clobber records with id ranging 
from [1] to [20]?

The confusion stemmed about from the fact that if you provide blank 
brackets when rendering an edit form, such as:

<% for @comment in @post.comments %>
<%= text_field ''comment[]'', ''author''
%>
<%= text_field ''comment[]'', ''body'' %>
<% end %>

It will also generate similar looking HTML tags, and hence in that case 
the number enclosed within the square brackets do have some 
significance.

Thanks.

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

Woei Shyang wrote:
>><% for i in 1..20 do %>
>><%= text_field  :new_items, :product_code, :index => i %>
>><%= text_field  :new_items, :quantity, :index => i %>
>><% end %>
> My query with this is, would Rails look at the number enclosed within 
> the square brackets and subsequently clobber records with id ranging 
> from [1] to [20]?
> 
> The confusion stemmed about from the fact that if you provide blank 
> brackets when rendering an edit form, such as:
> 
> <% for @comment in @post.comments %>
> <%= text_field ''comment[]'', ''author''
%>
> <%= text_field ''comment[]'', ''body''
%>
> <% end %>
> 
> It will also generate similar looking HTML tags, and hence in that case 
> the number enclosed within the square brackets do have some 
> significance.
While the parameter hash would be similar, with id rather than index keys,
you would handle it differently in the controller.  The Agile book suggests

     Cart.update(params[:new_items].keys, params[:new_items].values)

In the code I''ve given, the keys aren''t even looked at.  New
records
with new ids are created based on the hash values.

Looking over the code I see a few errors: The save of @user is not needed,
and flash.now should be used, not just flash. Also, for greater efficiency,
each new item should be instantiated via @user.items.build(p), then, if all
pass validation, saved using save(false), avoiding a second validation.

-- 
We develop, watch us RoR, in numbers too big to ignore.

Mark Reginald James wrote:
> 
> Perhaps:
> 
> <% for i in 1..20 do %>
> <%= text_field  :new_items, :product_code, :index => i %>
> <%= text_field  :new_items, :quantity, :index => i %>
> <% end %>
> 
> 
> case request.method
>    when :get then @new_items = Array.new(20) { Cart.new }
>    when :post
>      all_valid = true
>      @new_items = []
>      params[:new_items].each_value { |p| @new_items <<
(c=Cart.new(p));
> all_valid &&= c.valid? }
>      if !@new_items.empty? && all_valid
>         @user.items << @new_items
>         @user.save(false)
>         redirect_to :action => ''show_cart''
>      else
>        flash[:error] = ''No items entered'' if
@new_items.empty?
>        (20-@new_items.length).times { @new_items << Cart.new }
>      end
> end

Is this method going to flow any validation errors back to the form 
though?  If it was just one new item on the form you could use:

  <%= error_messages_for ''new_items'' %>

but I''m not clear on whether that would work with this method. 
Doesn''t
it end up just like it would using non-model objects on the form and 
placing the data into Cart objects in the controller?  Works, but the 
form doesn''t show the validation messages.


-- 
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Shawn Goble wrote:
> Mark Reginald James wrote:
>> [CODE]
> 
> Is this method going to flow any validation errors back to the form 
> though?  If it was just one new item on the form you could use:
> 
>   <%= error_messages_for ''new_items'' %>
> 
> but I''m not clear on whether that would work with this method. 
Doesn''t
> it end up just like it would using non-model objects on the form and 
> placing the data into Cart objects in the controller?  Works, but the 
> form doesn''t show the validation messages.
All fields with errors will be highlighted, but to get the text
messages you''ll need something like:

<% for i in 1..20
    @item = @new_items[i-1] %>
Item <%= i %>: <%= error_messages_for :item %>
<% end %>

-- 
We develop, watch us RoR, in numbers too big to ignore.

Mark Reginald James wrote:
> case request.method
>    when :get then @new_items = Array.new(20) { Cart.new }
>    when :post
This still seems not to work.

If in the controller I use:

  @new_items = Cart.new

then the :index in the template seems to work correctly (even though 
I''ve only created one object in the controller).  It will even save the
information to the database correctly using that method.  The downside 
is that I still can''t get validation error information back to the
form.

If however, I do as you suggest (which does seem to make more sense) and 
use:

  @new_items = Array.new(20) { Cart.new }

I get the error "undefined method `product_id'' for
#<Array:0x55dae60>",
which seems to suggest that :index isn''t actually letting me reference 
an array but creating one after the fact from a single object. 
(Incidentally, if I use @new_items = Cart.new and then after :post I 
eventually use something like @new_items = Cart.create(items), I get the 
same error "undefined method `product_id'' for
#<Array:0x55dae60>" in the
template.)

Thanks for the help so far, I''ve at least learned something about the 
:index parameter.


-- 
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Shawn Goble wrote:
> If in the controller I use:
> 
>   @new_items = Cart.new
> 
> then the :index in the template seems to work correctly (even though 
> I''ve only created one object in the controller).  It will even
save the
> information to the database correctly using that method.  The downside 
> is that I still can''t get validation error information back to the
form.
> 
> If however, I do as you suggest (which does seem to make more sense) and 
> use:
> 
>   @new_items = Array.new(20) { Cart.new }
> 
> I get the error "undefined method `product_id'' for
#<Array:0x55dae60>",
> which seems to suggest that :index isn''t actually letting me
reference
> an array but creating one after the fact from a single object. 
Yes, sorry, the :index parameter does not do what I thought it did.
It replicates form fields and parameters from a single model instance,
which is not useful for the multiple instances with validation errors
situation you are looking for.

You may be able to make it work using some trick like:

<% @new_items.each_with_index do |@cart, i| %>
<%= text_field :cart, :product_id, :name =>
"cart[#{i}][product_id]" %>
<% end %>

-- 
We develop, watch us RoR, in numbers too big to ignore.