Rails - Aug 2009 - Re-initialising page after validation fails

Hi,

I have a controller and two of the actions in it are as follows:

  # GET /bids/new
  # GET /bids/new.xml
  def new
    @bid = Bid.new
    @auctionItems = AuctionItem.find(:all)

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @bid }
    end
  end

  # GET /bids/1/edit
  def edit
    @bid = Bid.find(params[:id])
  end

  # POST /bids
  # POST /bids.xml
  def create
    @bid = Bid.new(params[:bid])

    respond_to do |format|
      if @bid.save
        flash[:notice] = ''Bid was successfully created.''
        format.html { redirect_to(@bid) }
        format.xml  { render :xml => @bid, :status => :created,
:location => @bid }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @bid.errors, :status =>
:unprocessable_entity }
      end
    end
  end

The new.html.erb contains this line:

<%= f.select(:auction_item_id, @auctionItems.collect {|i| [ i.title,
i.id ]

Which populates a select with the auctionItems fetched in the new
action.

If validation fails in the "create", I get an error something like:

 NoMethodError in Bids#create

Showing app/views/bids/new.html.erb where line #8 raised:

You have a nil object when you didn''t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.collect

Extracted source (around line #8):

5:
6:
7: <p>
8: <%= f.select(:auction_item_id, @auctionItems.collect {|i| [ i.title,
i.id ] }, { :include_blank => true }) %>
9: </p>
10:
11: <p>

I am guessing this is because the auctionItems is not repopulated for
this request.

So, does this:

        format.html { render :action => "new" }

Mean it only displays new.html.erb, and not re-runs the "new" action?

What is the best way to ensure that @auctionItems gets repopulated.  I
suppose I modify create like this:

  def create
    @bid = Bid.new(params[:bid])

    respond_to do |format|
      if @bid.save
        flash[:notice] = ''Bid was successfully created.''
        format.html { redirect_to(@bid) }
        format.xml  { render :xml => @bid, :status => :created,
:location => @bid }
      else
        @auctionItems = AuctionItem.find(:all)
        format.html { render :action => "new" }
        format.xml  { render :xml => @bid.errors, :status =>
:unprocessable_entity }
      end
    end
  end

But it doesn''t seem the best practice.  Is there a better way to do
this?  I have seen some mention of "Helpers" - is this something they
could be used for?

Many thanks,
Andrew.
-- 
Posted via http://www.ruby-forum.com/.

On Aug 8, 7:20 am, Andrew Myers
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> If validation fails in the "create", I get an error something
like:
>
>  NoMethodError in Bids#create
>
> Showing app/views/bids/new.html.erb where line #8 raised:
>
> You have a nil object when you didn''t expect it!
> You might have expected an instance of Array.
> The error occurred while evaluating nil.collect
>
> Extracted source (around line #8):
>
> 5:
> 6:
> 7: <p>
> 8: <%= f.select(:auction_item_id, @auctionItems.collect {|i| [ i.title,
> i.id ] }, { :include_blank => true }) %>
> 9: </p>
> 10:
> 11: <p>
>
> I am guessing this is because the auctionItems is not repopulated for
> this request.
>
> So, does this:
>
>         format.html { render :action => "new" }
>
> Mean it only displays new.html.erb, and not re-runs the "new"
action?
Yep - all that does is render the selected template. The idea is that
that the form will be redisplayed with the contents of @bid.
>
> What is the best way to ensure that @auctionItems gets repopulated.  I
> suppose I modify create like this:
>
>   def create
>     @bid = Bid.new(params[:bid])
>
>     respond_to do |format|
>       if @bid.save
>         flash[:notice] = ''Bid was successfully created.''
>         format.html { redirect_to(@bid) }
>         format.xml  { render :xml => @bid, :status => :created,
> :location => @bid }
>       else
>         @auctionItems = AuctionItem.find(:all)
>         format.html { render :action => "new" }
>         format.xml  { render :xml => @bid.errors, :status =>
> :unprocessable_entity }
>       end
>     end
>   end
>
> But it doesn''t seem the best practice.  Is there a better way to
do
> this?  I have seen some mention of "Helpers" - is this something
they
> could be used for?
>
This is a very typical use of helpers - you could put this code into
app/helpers/bid_helper.rb:

def auction_select(form)
  form.select(:auction_item_id, AuctionItem.all.collect {|i|
[ i.title,
i.id ] })
end

and then call it from your views as:

<%= auction_select(f) %>

It tidies things up, and then when you need to select an auction
someplace else, it can be reused.

BTW, mixed-case variable names are nonstandard in Rails - normally,
you use underscored names (@auction_items rather than @auctionItems).
No real difference, but it looks odd to experienced programmers.

--Matt Jones

Thanks Matt - that sounds like the solution I am after.  Also thanks for 
the advice re variable names.  I am coming to Ruby from Java and have a 
bit to learn in that regard. :-)

Matt Jones wrote:
> 
> This is a very typical use of helpers - you could put this code into
> app/helpers/bid_helper.rb:
> 
> def auction_select(form)
>   form.select(:auction_item_id, AuctionItem.all.collect {|i|
> [ i.title,
> i.id ] })
> end
> 
> and then call it from your views as:
> 
> <%= auction_select(f) %>
> 
> It tidies things up, and then when you need to select an auction
> someplace else, it can be reused.
> 
> BTW, mixed-case variable names are nonstandard in Rails - normally,
> you use underscored names (@auction_items rather than @auctionItems).
> No real difference, but it looks odd to experienced programmers.
> 
> --Matt Jones
-- 
Posted via http://www.ruby-forum.com/.