Hi David,
Yes, the expansion I essentially want, and which runs properly without
the macro:
(proxy [EWrapper] []
(tickPrice [& args] (println "tickPrice" (. EWrapperMsgGenerator
tickPrice args)))
(tickSize [& args] (println "tickSize" (. EWrapperMsgGenerator
tickSize args)))
... other methods
)
I resorted to a macro because there are 20-30 different methods, and
if I wanted to write boilerplate all day I'd just do it in pure
Java :)
I'm sure there are other approaches like using reflection, or pulling
out the inner (println ...) form into another macro, but this pretty
well-defined.
Thanks,
Jian
On Jun 18, 10:52 am, David Nolen <dnolen.li...@gmail.com> wrote:
> On Fri, Jun 17, 2011 at 11:51 PM, Jian Liu <liuj...@gmail.com> wrote:
> > Hi Clojure Gurus :)
>
> > I've a somewhat contrived use-case for macros that I've been
> > struggling with.
>
> > Let's say there's an interface called EWrapper that I'm trying to
> > implement with methods "tickPrice" and "tickSize", a concrete class
> > EWrapperMsgGenerator that has methods with those names that return
> > strings.
>
> > I'd like to write a macro that proxies EWrapper's tickSize and
> > tickPrice methods so that they print out the method name as well as
> > the string returned from EWrapperMsgGenerator.
>
> > E.g. (in java code):
> > public tickSize( args ) { // on the proxied EWrapper
> > System.out.println( "tickSize: " +
> > EWrapperMsgGenerator.tickSize( args ) )
> > }
>
> > Here's what I've come up with so far:
>
> > (defmacro make-msg-ewrapper [method-names]
> > `(proxy [EWrapper] []
> > ~@(map
> > (fn [method-name]
> > `(~(symbol method-name) [& args#]
> > (println ~method-name ":"
> > (. EWrapperMsgGenerator ~(symbol method-name)
> > args#))))
> > method-names)))
>
> > It's a bit messy -- I'm splicing in a map evaluation into proxy, and
> > then writing in symbols in the function body. This works except that
> > when I run the macro I get "No matching method: tickSize" referring to
> > EWrapperMsgGenerator.
>
> > The macro expansion looks like:
>
> > (let* [p__4736__auto__ (new user.proxy$java.lang.Object$EWrapper
> > $11bc5609)] (clojure.core/init-proxy p__4736__auto__ {tickPrice
> > (clojure.core/fn ([this & args__2058__auto__] (clojure.core/println
> > tickPrice : (. com.ib.client.EWrapperMsgGenerator tickPrice
> > args__2058__auto__)))), list (clojure.core/fn ([this &
> > args__2058__auto__] (clojure.core/println list : (.
> > com.ib.client.EWrapperMsgGenerator list args__2058__auto__))))})
> > p__4736__auto__)
>
> > So far this looks fine to me, except that tickPrice within the
> > EWrapperMsgGenerator call isn't scoped. Is there a better way to do
> > this?
>
> > Thanks,
> > Jian
>
> Do you have a working version of the code you want that doesn't involve a
> macro?
>
> David
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