well :title and :visible are not the only ones i want to support, i would like something that would work with any keyword and convert it to the right setter.
you are right about the need for a let. i've been away from lisp for a while, and i forgot about this sort of thing. but will a let fix my evaluation problem? On Oct 27, 6:00 pm, mb <[EMAIL PROTECTED]> wrote: > Hi, > > On 27 Okt., 21:08, Matt Moriarity <[EMAIL PROTECTED]> wrote: > > > > > I am trying to write a macro to rewrite something like this: > > > (set-props my-jframe :title "blah" :visible true) > > > Into calls to the setter methods. I finally settled on this: > > > (defmacro set-props [obj & props] > > (let [prop-map (apply hash-map props)] > > `(do > > ~(for [[key val] prop-map] > > `(~(keyword-to-method key) ~obj ~val)) > > ~obj))) > > > where keyword-to-method just converts :title into .setTitle. > > ... > > how can i make this work? > > You probably don't need a macro here. > > (use '[clojure.contrib.fcase :only (case)]) > > (defn keyword-to-method > [kw] > (case kw > :title #(. %1 setTitle %2) > :visible #(. %1 setVisible %2))) > > (defn set-props > [obj & props] > (do > (doseq [k v] (partition 2 props) > ((keyword-to-method k) obj v)) > obj)) > > This is a pretty naive implementation, but it should probably > work. > > Just a note about your macro. You should not insert the same > value several times. It will be evaluated several times. Imagine > you call your macro as (set-props (new JFrame) ...). The object > actually returned is a different JFrame! > > The correct way is to use a let. > > (defmacro xxx > [obj] > `(let [obj# ~obj] > (do-stuff-with obj#) > (and-more-stuff obj#))) > > Now the obj is just evaluated once. symbol# is a short way to > generate a unique symbol, which can be used to cache the value. > > Hope this helps. > > Sincerely > Meikel --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
