#791 Add empty_template option when rendering a collection - Ruby on Rails

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#791 ✓resolved

Add empty_template option when rendering a collection

Reported by Frederick Cheung | August 9th, 2008 @ 03:34 PM | in 2.x

I'm sick of writing

@@@ lang=ruby <% if search_results.empty? %> Nothing found <% else %> <%= render :partial => 'search_result', :collection => search_results %> <% end %>



As far as I'm concerned the less actual code  and branching in views, the better. Instead I propose

<%= render :partial => 'search_result', :collection => search_results, :empty_template => 'nothing_found' %>



With the nothing_found partial containing the obvious. (I'd rather have a better option name than empty_template but I haven't thought of one so far)

0001-Allow-render-partial-to-specify-an-alternate-templa.patch 5.5 KB

Comments and changes to this ticket

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RSL August 13th, 2008 @ 01:54 PM
+1 especially with the option for handling simple one line HTML strings [as discussed in #rails-contrib].

Frederick Cheung August 13th, 2008 @ 08:09 PM

Revised version of the patch. use cases now include


render :partial => 'record', :collection => @records, :empty => 'Nothing found'
render :partial => 'record', :collection => @records, :empty => {:partial => 'nothing_found'}
render :partial => 'record', :collection => @records, :empty => {:inline => '<%= @something %>'}

0001-Add-the-empty-option-when-rendering-collections.patch 7.1 KB

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Steven Bristol August 14th, 2008 @ 01:09 PM
I like this concept a lot, but I am wondering if it might not be better to have render take a block that is used if the collection is empty? I'm not sure that makes sense for the other uses of render, but I prefer that syntax over supplying html as a string.
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Ryan Bates August 15th, 2008 @ 03:54 PM
BTW, a discussion of this can be found at this thread.
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Ryan Bates August 15th, 2008 @ 04:40 PM
In this thread some have come to the conclusion that it would be best if "render :collection" returned nil instead of a space for an empty array. This way you can do this with a simple "or" operation.
```
<%= render :partial => @records || "Nothing found" %>
```
Attached is a patch which does this. I moved some stuff around, so that whenever you're trying to render nil, a space is used in the response body so Safari doesn't complain. This way it happens later on in the response chain so "render :collection" doesn't have to be concerned with it.
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Ryan Bates August 15th, 2008 @ 04:49 PM
Correction: you'll need to wrap the render call in parenthesis.
```
<%= render(:partial => @records) || "Nothing found" %>
```
Eloy Duran August 15th, 2008 @ 05:43 PM
+1 for Ryans patch. Seems the best Ruby-ish solution.
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RSL August 15th, 2008 @ 06:05 PM
What about the case where you want something more complex than a simple string rendered when the collection is empty?

Damian Janowski August 15th, 2008 @ 06:17 PM

RSL,


<%= render(:partial => @records) || render_very_complex_logic_found_in_helpers__of_course %>

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Damian Janowski August 15th, 2008 @ 06:19 PM
Ryan, why not checking for collection.blank? so that it doesn't fail with nils? Other than that I'm +1.
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Ryan Bates August 15th, 2008 @ 06:39 PM
@RSL, as Damian mentioned you can toss it into a helper. Or you can just render a partial right here.
```
<%= render(:partial => @records) || render(:partial => 'empty') %>
```
@Damian, I tried this briefly but it still errors out with nil. I don't think the fix is that simple so it should probably go in its own ticket.
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Ryan Bates August 15th, 2008 @ 07:08 PM
Nevermind, found the problem. Attached is an updated patch which also returns nil when nil is passed.
- render_empty_collection_or_nil_returns_nil.diff 4.4 KB
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Damian Janowski August 15th, 2008 @ 07:34 PM
Great :-)

Tests pass and there's no need for doc changes.

+1
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RSL August 15th, 2008 @ 07:40 PM
@ ryan & damien, doy. where is my mind? i like this.
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S. Brent Faulkner August 15th, 2008 @ 09:53 PM
+1 for render_empty_collection_or_nil_returns_nil.diff

definitely.
josh August 19th, 2008 @ 05:43 AM
- State changed from “new” to “open”
- Assigned user set to “josh”
+1 to returning just returning nil
Repository August 20th, 2008 @ 01:09 AM
- State changed from “open” to “resolved”
(from [a8ece12fe2ac7838407954453e0d31af6186a5db]) Return nil instead of a space when passing an empty collection or nil to 'render :partial' [#791 state:resolved]

Signed-off-by: Joshua Peek josh@joshpeek.com http://github.com/rails/rails/co...
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Andrew Vit November 6th, 2008 @ 10:31 AM
Just a note, this change crashes XML builder templates with empty collections which use this convention:
```
@items = []
xml << render( :collection => @items )
```
This is because Builder's << operator won't accept nil, and it throws a "can't convert nil to String" error. The easiest workaround seems to be as above, using the || operator with an empty string, but that sure looks funky:
```
xml << ( render(:collection => @items) || '' )
```
Or else pass in a :locals option and don't use the << convention:
```
render( :collection => @items, :locals => {:x => xml} )
```
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