Url_for_file_column not works

Rails
1

I am using the file column plugin.

If i upload an image it works correctly but if i want to show an image
it not works.

in my template i insert

url_for_file_column(@core, “image”, “thumb”)

but return “”

i tried to print @core.image but it is set to nil.

My model is this:

class Core < ActiveRecord::Base
has_one :forum_topic
has_many :votes
has_many :forum_messages ,:through => :forum_topic
attr_accessible :site,:descriptionm,:image
file_column :image,:magick=>{
:geometry=>‘600x600>’,:attributes => { :quality => 60 },
:versions => {
:thumb => {:crop => “1:1”, :geometry =>“30x30”,:attributes => {
:quality => 50 } },
:thumb_big=>{:crop => “1:1”, :geometry =>“62x62”,:attributes =>
{ :quality => 50 } }
}
}
}

How i can do?
Thanks

2

I have noted that if i do it:
url_for_file_column(Core.find(cores.id), “image”)
it works.

but if i use url_for_file_column in a template called with:

<%=render(:partial =>
“what”,:collection=>Core.find(:all,:conditions=>“id<10”))%>

and content:
url_for_file_column(what, “image”)

it not works.
Why?