Insertions into Zipper trees on XML files in Clojure
- by ivar
I'm confused as how to idiomatically change a xml tree accessed through clojure.contrib's zip-filter.xml. Should be trying to do this at all, or is there a better way?
Say that I have some dummy xml file "itemdb.xml" like this:
<itemlist>
<item id="1">
<name>John</name>
<desc>Works near here.</desc>
</item>
<item id="2">
<name>Sally</name>
<desc>Owner of pet store.</desc>
</item>
</itemlist>
And I have some code:
(require '[clojure.zip :as zip]
'[clojure.contrib.duck-streams :as ds]
'[clojure.contrib.lazy-xml :as lxml]
'[clojure.contrib.zip-filter.xml :as zf])
(def db (ref (zip/xml-zip (lxml/parse-trim (java.io.File. "itemdb.xml")))))
;; Test that we can traverse and parse.
(doall (map #(print (format "%10s: %s\n"
(apply str (zf/xml-> % :name zf/text))
(apply str (zf/xml-> % :desc zf/text))))
(zf/xml-> @db :item)))
;; I assume something like this is needed to make the xml tags
(defn create-item [name desc]
{:tag :item
:attrs {:id "3"}
:contents
(list {:tag :name :attrs {} :contents (list name)}
{:tag :desc :attrs {} :contents (list desc)})})
(def fred-item (create-item "Fred" "Green-haired astrophysicist."))
;; This disturbs the structure somehow
(defn append-item [xmldb item]
(zip/insert-right (-> xmldb zip/down zip/rightmost) item))
;; I want to do something more like this
(defn append-item2 [xmldb item]
(zip/insert-right (zip/rightmost (zf/xml-> xmldb :item)) item))
(dosync (alter db append-item2 fred-item))
;; Save this simple xml file with some added stuff.
(ds/spit "appended-itemdb.xml"
(with-out-str (lxml/emit (zip/root @db) :pad true)))
I am unclear about how to use the clojure.zip functions appropriately in this case, and how that interacts with zip-filter.
If you spot anything particularly weird in this small example, please point it out.
