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From: wjs@milton.u.washington.edu (William Shipley)
Newsgroups: comp.sys.next
Subject: Re: Run-time object loading
Message-ID: <6326@milton.u.washington.edu>
Date: 15 Aug 90 00:03:40 GMT
References: <1990Aug13.223632.312@svc.portal.com>
Organization: University of Washington, Seattle
Lines: 34

In article <1990Aug13.223632.312@svc.portal.com> moose@svc.portal.com writes:
>
>	I am looking for a way to dynamically load objects at run-time.  I want
>an application that can allow people to drop in their own custom objects 
>whenever they want to.  I know how to drop in interface files, I don't know 
>how to drop in raw objects.  

Currently it's pretty easy to dynamically load functions, but pretty
difficult to dynamically load objects.

Functions are easy because all you need is a pointer to them and you
can call them.  Here at Stanford Linear Accelerator I have created a
set of routines which allow the user to dynamically link in functions:
it took about 2 pages of code.  (Available on request.)

For objects, it depends on what you mean by "object".  If you want to drop
in an object of an already existing (in the target program) class, you
can just unarchive it (or do somehting similar).  If you want to dynamically
add a new class, it's harder, because you have to inform the run-time
Obj-C system all about your new class, including the size of the objects
and the methods they respond to.

This may be as easy as calling objc_addClass(), but, honestly, I have no
idea.

It hasn't been made clear to me whether 2.0 will actually support run-time
loading of new classes, or just run-time linking of new functions.

-william shipley
NeXT developer at Stanford Linear Accelerator
(student at University of Washington, too)

PS: Thanks should be given to Alan Marcum at NeXT for assistance getting
dynamic linking to work.