• Benji Smith <dlanguage xxagg.com> Dec 20 2004
• "Walter" <newshound digitalmars.com> Dec 20 2004
• pragma <pragma_member pathlink.com> Dec 21 2004
• Benji Smith <dlanguage xxagg.com> Dec 21 2004

I've been thinking about the Java Reflection API and how useful it can
be to change the behavior of an application during runtime. Even
though no such API exists right now for D, I've been looking at the D
ABI page ( http://www.digitalmars.com/d/abi.html ) and thinking that
it wouldn't be difficult for a third-party developer to write a
reflection API using the information from the object's classinfo
property and vtable. Even though much of the ABI is still marked as
TBD, if the ABI is anticipated to remain relatively stable, it would
be possible to build the reflection interface just by referring to the
object.d code in phobos.

Though, even if it would currently be possible to produce a reflection
API using this information, it wouldn't be worth the effort if the ABI
isn't set in stone yet.

So, Walter, how stable is the ABI right now?

--Benji Smith

"Benji Smith" <dlanguage xxagg.com> wrote in message
news:r2ses0t5bn16p40lv21d548dkph4c67p0h 4ax.com...
 I've been thinking about the Java Reflection API and how useful it can
 be to change the behavior of an application during runtime. Even
 though no such API exists right now for D, I've been looking at the D
 ABI page ( http://www.digitalmars.com/d/abi.html ) and thinking that
 it wouldn't be difficult for a third-party developer to write a
 reflection API using the information from the object's classinfo
 property and vtable. Even though much of the ABI is still marked as
 TBD, if the ABI is anticipated to remain relatively stable, it would
 be possible to build the reflection interface just by referring to the
 object.d code in phobos.

 Though, even if it would currently be possible to produce a reflection
 API using this information, it wouldn't be worth the effort if the ABI
 isn't set in stone yet.

 So, Walter, how stable is the ABI right now?


It's pretty well fixed now. I plan on extending classinfo, but that won't
change the existing layout and meaning of its current members.

In article <r2ses0t5bn16p40lv21d548dkph4c67p0h 4ax.com>, Benji Smith says...
Though, even if it would currently be possible to produce a reflection
API using this information, it wouldn't be worth the effort if the ABI
isn't set in stone yet.


If memory serves, someone had posted up an interim solution here to the NG
several months ago.  It was a custom tool that created reflection classes and
information from the map files that dmd generates.  I've tried searching the
archives, but I had no luck finding that particular post.

I think you're on the right track with coding against the ABI.  A preprocessor
would be the best approach, IMO, as there's only so much information you can
gather from within D at this point.  The map-file-based postprocessor approach
works too, but the resulting code doesn't mesh as well with the language as one
would like.

RT:
Since Walter is still planning on coding this feature into D properly, perhaps
now would be the best time to investigate possible solutions/approaches to
reflection in D.  Also, this NG has a history of such proposals, so the way
ahead may be pretty well mapped out.  At least that way, Walter would have the
benefit of the community's reaction before he sets out to put it into D
properly. ;)

- EricAnderton at yahoo

On Tue, 21 Dec 2004 15:34:42 +0000 (UTC), pragma
<pragma_member pathlink.com> wrote:
I think you're on the right track with coding against the ABI.  A preprocessor
would be the best approach, IMO, as there's only so much information you can
gather from within D at this point.


I think I'd rather focus on designing a really great reflection
interface and the coding as much of it up as possible. Whatever
remains impossible to code will act as a guide for what types of
additional features need to be available from the classinfo property
(and through the ABI).

I've started sketching together a REALLY skeletal reflection framework
on the wiki, here:

http://www.prowiki.org/wiki4d/wiki.cgi?ReflectionInD

Feel free to tinker with it and add your own suggestions and
improvements.

At the moment, it primarily includes methods for accessing information
about primitives, classes, objects (instances of those classes),
methods, etc. What it *doesn't* include yet are any functions for
using the reflection API to dynamically *generate* new classes and
objects at runtime (simply because I only spent an hour working on
it).

--Benji