ruby on rails - default image for paperclip is not displayed -

while looping through objects in view trying display first attached image of listing this:

<%= image_tag listing.assets.first.attachment.url(:small) %> 

this works fine if listings have @ least 1 image if 1 listing doesn't have image, default image not shown. instead undefined method `attachment' nil:nilclass.

which logical because object nil have in model

has_attached_file :attachment, :styles => { :medium => "300x300>", :small => "200x200>", :thumb => "100x100>" }, :default_url => "no_image_:style.jpg" 

so assume if image_tag doesn't receive ai url should display "no_image_small.jpg" in app/assets/images folder.

is how should work? how can display no_image_small.jpg if image doesn't exist , nill?

im guessing have listing model looks this:

class listing < activerecord::base   has_many :assets   ... end 

and asset class this

class asset < activerecord::base   has_attached_file :attachment, :styles => { :medium => "300x300>",    :small => "200x200>", :thumb => "100x100>" },    :default_url => "no_image_:style.jpg"   ... end 

the problem not paperclip or setup, listing don't have associated assets.

edit:

here solution still default image, association:

<% asset = listing.assets.first || listing.assets.build %>  <%= image_tag asset.attachment.url(:small) %>