Add empty_template option when rendering a collection

+1 especially with the option for handling simple one line HTML strings [as discussed in #rails-contrib].

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 %>'}

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.

BTW, a discussion of this can be found at this thread.

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.

Correction: you'll need to wrap the render call in parenthesis.

<%= render(:partial => @records) || "Nothing found" %>

+1 for Ryans patch. Seems the best Ruby-ish solution.

What about the case where you want something more complex than a simple string rendered when the collection is empty?

RSL,

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

Ryan, why not checking for collection.blank? so that it doesn't fail with nils? Other than that I'm +1.

@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.

Nevermind, found the problem. Attached is an updated patch which also returns nil when nil is passed.

Great :-)

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

+1

@ ryan & damien, doy. where is my mind? i like this.

+1 for render_empty_collection_or_nil_returns_nil.diff

definitely.

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} )