On Jan 12, 1:50 am, Konrad Hinsen <konrad.hin...@fastmail.net> wrote:
> On 11 Jan 2010, at 23:09, .Bill Smith wrote:
>
> > Every class object has a newInstance method:
>
> > user=> (Class/forName "java.util.HashMap")
> > java.util.HashMap
> > user=> (.newInstance (Class/forName "java.util.HashMap"))
> > #<HashMap {}>
> > user=>
>
> > Is that what you are looking for?
>
> It seems close, but it doesn't work for me. From experimenting I have
> the impression that this works only for constructors with no arguments.
>
> I found some stuff in the Java docs on reflection that could work, but
> this is getting very complicated... I'll first see if I can do without.
>
> Thanks,
> Konrad.
I have this lying around for situations where I need to call an
arbitrary constructor:
(defn construct [desc]
(let [dclass (:class desc)
initargs (to-array (:initargs desc))
initclasses (make-array Class (count initargs))]
(doseq [i (range 0 (count initclasses))]
(aset initclasses i (class (aget initargs i))))
(let [constructor (. dclass (getConstructor initclasses))]
(if constructor
(. constructor (newInstance initargs))
(throw (Exception. (format "no %s constructor for args: %s"
(str dclass) (map str
initclasses))))))))
Why the rigamarole with make-array and aset, rather than to-array or
into-array? To ensure that I *always* get a Class[], even when the
input list is empty (the reflection calls are finicky about that).
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