Forum: Ruby on Rails How to reference parent object when using sub-resources

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Aa7c7271940f563b41cba57dc28028a1?d=identicon&s=25 POOCH (Guest)
on 2009-01-06 15:20
(Received via mailing list)
Hi,

I'm building my first Rails application and have hit a problem using
sub-resources.

My model includes a Deposit that has_many Payments.  So routes.rb has
a line:

       map.resources :deposits, :has_many => :payments

I've generated the scaffolding for Payments and I am able to go from a
particular Deposit to a page where I want to show its list of
Payments.  The index.html.erb for Payments begins with these 2 lines:

     <h2>Payments for deposit <%= @deposit.deposit_date %> : <%=
@deposit.name %></h2>

     <%= link_to 'Add a payment', new_payment_path(@deposit) %>

The references to @deposit in the first line are resolved correctly,
but not so on the second line.  When trying to render the index, the
error messages I get are:

     NoMethodError in Payments#index
     You have a nil object when you didn't expect it!
     The error occurred while evaluating nil.to_sym

This at first made me think that @deposit was nil when the second line
was parsed, but now I think that the first error line is more to the
point -- there isn't a new_payment_path method that takes a Deposit as
a parameter.  But I need to pass in the parent Deposit on the page
where I will be creating a child Payment, so how can I do that?

When I remove the @deposit parameter from new_payment_path, the page
renders fine, but when I click the Add a Payment link, the page it
goes to is http://localhost:3000/payments/new , with no reference to
the parent Deposit.

So how do I pass in the parent when creating the child?

Thanks!
Aa7c7271940f563b41cba57dc28028a1?d=identicon&s=25 POOCH (Guest)
on 2009-01-06 15:41
(Received via mailing list)
Nevermind -- I've found the answer.  The link_to should be coded as:

     <%= link_to 'Add a payment', new_deposit_payment_path(@deposit)
%>

For me, magic is often hard to follow.
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