clone-for.clj

;; answer to what I understood of http://d.hatena.ne.jp/fatrow/20100407/1270662784

;; your original code
(en/defsnippet lib-model "src/html/a.html" [:.library]
  [{:keys [name description url category]}]
  [:.name] (en/content name)
  [:.descriptionj] (en/content description)
  [:.site :a] (en/do-> (en/set-attr :href url)
                       (en/content url))

(en/deftemplate libpage "src/html/a.html"
  [libdata]
  [:.library] (en/substitute (map lib-model libdata)))

;; rewritten with clone-for:
(en/deftemplate libpage "src/html/a.html"
 [libdata]
  [:.library] (clone-for [{:keys [name description url category]} lib-data] 
                [:.name] (en/content name)
                [:.descriptionj] (en/content description)
                [:.site :a] (en/do-> (en/set-attr :href url)
                              (en/content url))))

;; clone-for first vector is a seq comprehension (like in #'for) and its body consists of pairs of selectors/transformations
;; so clone-for clones the elements selected by [:.library] as many times there are items in lib-data and then each clone is
;; transformed according to the selectors/transformations specified as body of the clone-for form.