Getting url for an attachment

I'm using CouchApp to build an easy web application that allows to upload and manage pictures. The actual image file is stored as attachment to the doc like show below.

{
  "_id":"09fe82d75a26f9aa5e722d6b220180d2",
  "_rev":"2-5797b822c83b9d41545139caa592f611",
  "data":"some additional fields with info about the image",
  "_attachments":
  {
    "foo.jpg":
    {
      "stub":true,
      "content_type":"image/jpeg",
      "length":23721
    }
  }
}

But for integrating the image in html i need the url to the attachment. How do i get this url?

I'm using evently and mustache for generating the web pages. Below is the data.js for reading the data:

function(data) {
  return {
    items : data.rows.map(function(r) {
      return {
        id : r.value._id,
        rev : r.value._rev,
        title : r.value.description,
        url : "how am i supposed to do this?"
      };
    })
  };
};

The URL to the attachment would be http://domain/database/09fe82d75a26f9aa5e722d6b220180d2/foo.jpg

If your filenames are dynamic, you would have to iterate the _attachments object and fetch the keys on your way - that's where your filename would be.

for(var filename in r.value._attachments){break;}
// ...
url : '<database>/' + r.value._id +'/'+filename;