Rails - Jul 2006 - Insert multiple new child records with the parent

Hello,

I am implementing a classic invoice application. On the create new 
invoice page
I want to allow users to add new line items using AJAX:

-----------------------------------------------------------------------------
Invoice Date  [            ]
Client        [            ]

Line Items
  1. [              ] $[    ]
  <add new line item>

<save> <cancel>
-----------------------------------------------------------------------------

When the user clicks on the <add new line item> link I would like to add 
a new
empty line item below the first using AJAX, without saving anything to 
the
database. A line item consists of a description and a price.

I want the line items, on save, to be passed to the controller as an 
array,
e.g., [{''description'' => ''line a'',
''cost'' => ''100''},
{''description'' =>
''line
b'', ''cost'' => ''200''}]. I
can''t find the correct naming convention for
the
textboxes to produce this data structure in the controller.

I have tried:
<%= text_field_tag("line_items[0][description]") %>
<%= text_field_tag("line_items[0][cost]") %>
<%= text_field_tag("line_items[1][description]") %>
<%= text_field_tag("line_items[1][cost]") %>

which results in a hash of hashes:
"invoice_default"=>{"0"=>{"cost"=>"100",
"description"=>"line a"},
"1"=>{"cost"=>"200",
"description"=>"line b"}}

The problem with the hash of hashes is that I need to give each new line 
item
a key. Because the line items don''t yet exist in the database I have to
give
them an artificial key, a sequential number. It is then tricky to find 
the last
number in the sequence in order to add a new empty line item via AJAX.

I have also tried:
<%= text_field_tag("line_items[][description]") %>
<%= text_field_tag("line_items[][cost]") %>
<%= text_field_tag("line_items[][description]") %>
<%= text_field_tag("line_items[][cost]") %>

This results in a hash of hashes with a zero length string as the key, 
e.g,
{""=>{"cost"=>"100",
"description"=>"line a"}} and only the first line
item
is passed to the controller.

Does anyone have any ideas on how to solve this the rails way, i.e., 
elegantly?
I''m sure I am missing something terribly obvious.

Any help would be appreciated. I''ll write up a wiki entry on this 
problem if
anyone has a solution.

I apologise if this has already been discussed on the list. Both the 
gmane and
forum bridge searches are down.

Thanks,
Mark

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

Mark wrote:
> Hello,
> 
> I am implementing a classic invoice application. On the create new 
> invoice page
> I want to allow users to add new line items using AJAX:
> 
>
-----------------------------------------------------------------------------
> Invoice Date  [            ]
> Client        [            ]
> 
> Line Items
>   1. [              ] $[    ]
>   <add new line item>
> 
> <save> <cancel>
>
-----------------------------------------------------------------------------
> 
> When the user clicks on the <add new line item> link I would like to
add
> a new
> empty line item below the first using AJAX, without saving anything to 
> the
> database. A line item consists of a description and a price.
> 
> I want the line items, on save, to be passed to the controller as an 
> array,
> e.g., [{''description'' => ''line a'',
''cost'' => ''100''},
{''description'' =>
> ''line
> b'', ''cost'' => ''200''}]. I
can''t find the correct naming convention for
> the
> textboxes to produce this data structure in the controller.
> 
> I have tried:
> <%= text_field_tag("line_items[0][description]") %>
> <%= text_field_tag("line_items[0][cost]") %>
> <%= text_field_tag("line_items[1][description]") %>
> <%= text_field_tag("line_items[1][cost]") %>
> 
> which results in a hash of hashes:
>
"invoice_default"=>{"0"=>{"cost"=>"100",
"description"=>"line a"},
> "1"=>{"cost"=>"200",
"description"=>"line b"}}
> 
> The problem with the hash of hashes is that I need to give each new line 
> item
> a key. Because the line items don''t yet exist in the database I
have to
> give
> them an artificial key, a sequential number. It is then tricky to find 
> the last
> number in the sequence in order to add a new empty line item via AJAX.
> 
> I have also tried:
> <%= text_field_tag("line_items[][description]") %>
> <%= text_field_tag("line_items[][cost]") %>
> <%= text_field_tag("line_items[][description]") %>
> <%= text_field_tag("line_items[][cost]") %>
> 
> This results in a hash of hashes with a zero length string as the key, 
> e.g,
> {""=>{"cost"=>"100",
"description"=>"line a"}} and only the first line
> item
> is passed to the controller.
> 
> Does anyone have any ideas on how to solve this the rails way, i.e., 
> elegantly?
You can''t get params in the single array form you want it, but you
can get a pair of description and cost arrays using

<%= text_field_tag("line_items[description][]") %>
<%= text_field_tag("line_items[cost][]") %>

which you can then collate into single object attribute sets.

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