Re: [xmlvm-users] NSObject dispatchObject

[Paul P. <bay...@gm...>]

I'm going to go off on a tangent here, not really directed at this
conversation, but somewhat relevant.

My opinion is that reflection is a necessary evil that should be avoided
whenever possible.  One of the key words in that is "necessary."  A great
use of reflection is for web services or other generated code.  And that
equivalent is appropriately used in XMLVM.  I believe it is okay in this
type of situation because all parts using reflection are generated & not
typed by hand.  E.g. a web service is generated & a client is generated, so
if an update occurs, we just regenerate.

The "evil" part, in my opinion, comes when developers are manually typing
method names & class names into Strings, thus avoiding the compiler.  This
is unfortunately not a rarity in the real world, such as in configuration
files.  My hope is that as annotations gain muster, they will help squash
that practice where they can.

I realize there are exceptions to what I just said, but I still try to avoid
it at all costs.  Since reflection is learned at a more advanced stage, it
seems it is sometimes considered advantageous & advanced to use it, but I
believe that to be a misconception.

Anyways, I am not trying to contradict anything in this email chain, but
rather just get on my soapbox about "evil" reflection & have a conversation
in general.  I'm interested if anyone has some other thoughts on this.

Paul



On Fri, May 20, 2011 at 2:10 AM, Panayotis Katsaloulis <
pan...@pa...> wrote:

>
> On May 20, 2011, at 9:56 AM, Arno Puder wrote:
>
>
> hmm. Do you want to be able to call arbitrary *methods* or a certain
> method on arbitrary *objects*? For the former you need reflected, for
> the latter not. Actually, take a look at [DispatcherObject run] (in
> NSObject.m) to get an idea how you can invoke a Java method from C code.
>
>
>
> certain method, arbitrary objects.
> I did, I actually found these two parts:
> java_lang_reflect_Method* method = (*(JAVA_OBJECT (*)(JAVA_OBJECT,
> JAVA_OBJECT, JAVA_OBJECT)) targetClass->tib->vtable[
> XMLVM_VTABLE_IDX_java_lang_Class_getMethod___java_lang_String_java_lang_Class_1ARRAY])(targetClass,
> methodName, paramTypes);
> and
>  (*(JAVA_OBJECT (*)(JAVA_OBJECT, JAVA_OBJECT, JAVA_OBJECT)) method->tib->
> vtable[
> XMLVM_VTABLE_IDX_java_lang_reflect_Method_invoke___java_lang_Object_java_lang_Object_1ARRAY])(method,
> target, params);
> but I am a bit confused how to decode it.
> Moreover it seems that they use reflection - that's why I asked.
>
>
> And a last probably silly question:
>
> How do I convert an ObjC String to java_lang_String ?
>
> (and for completeness and back?)
>
>
> NSString* toNSString(JAVA_OBJECT o)
> JAVA_OBJECT toJavaString(NSString* str)
>
> both defined in NSString.m
>
>
> Oh , I missed that part - I was looking under java_lang_String :)
>
>
>
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