Problems subclassing from Agent2D (hello-world app)

[Paul Box]

Hello Group

Here is the problem that I'm having.  I have some code that I am
trying to update.  As the code involves a number of agents moving
around on an object dervived from a Discrete2d, I decided that it
would be well to rewrite the agents so that they are subclassed
fromAgent2D, a class in Barry M's hello-world application.  The agents
originally were derived from SwarmObjects, so I figured that deriving
them from Agent2D's should present no major problems, and make the
agents more "standardized"(the Agent2D is derived from a swarmobject
itself, with just a few funcions added on).

Originially, the agents, called "Boats", were declared in Boat.h as
such:

#import <objectbase.h>
#import <objectbase/SwarmObject.h>

@interface Boat: SwarmObject { ....


I changed the header file with the following lines:

#import "Agent2D.h"

@interface Boat: Agent2d { ...


And replaced some of the internal functions of the Boat with calls to
functions that it inherited from being an Agent2D.

Agent2D.h has the following lines:

#import <objectbase.h>
#import <objectbase/SwarmObject.h>

@interface Agent2D: SwarmObject { ...



The code seems to parse fine, but after the object files are built, I
get the following error in linking:


franklin:~/swarm/projects/floatspaceF> make
gcc -c -Wno-import -g -O2 -D_GNU_SOURCE -I/usr/local/include Boat.m   
gcc -c -Wno-import -g -O2 -D_GNU_SOURCE -I/usr/local/include
AnchorModelSwarm.m   
/usr/local/bin/libtool-swarm --mode link gcc -g -O2 -L/usr/local/lib
-Wl,-rpath /usr/local/lib    -L/usr/local/lib -Wl,-rpath
/usr/local/lib -L/usr/local/lib -Wl,-rpath /usr/local/lib -L/usr/lib
-Wl,-rpath /usr/lib -L/usr/X11R6/lib  -o floatspace main.o Boat.o
AnchorModelSwarm.o AnchorObserverSwarm.o Cell.o CellSurface.o
DataFile.o Eneighbor.o CellProbe.o SeaBug.o DataFileSwarm.o  -lspace
-lanalysis -lsimtools -lsimtoolsgui -ltkobjc -ltclobjc -lactivity
-lrandom -lobjectbase -lcollections -ldefobj -lmisc -lBLT -ltk8.0
-ltcl8.0 -lpng -lz -lffi -lXpm -lX11  -lm -lobjc -ldl 
gcc -g -O2 -L/usr/local/lib -Wl,-rpath /usr/local/lib -L/usr/local/lib 
-Wl,-rpath /usr/local/lib -L/usr/local/lib -Wl,-rpath /usr/local/lib
-L/usr/lib -Wl,-rpath /usr/lib -L/usr/X11R6/lib -o floatspace main.o
Boat.o AnchorModelSwarm.o AnchorObserverSwarm.o Cell.o CellSurface.o
DataFile.o Eneighbor.o CellProbe.o SeaBug.o DataFileSwarm.o -lspace
-lanalysis -lsimtools -lsimtoolsgui -ltkobjc -ltclobjc -lactivity
-lrandom -lobjectbase -lcollections -ldefobj -lmisc -lBLT -ltk8.0
-ltcl8.0 -lpng -lz -lffi -lXpm -lX11 -lm -lobjc -ldl
Boat.o: In function `_i_Boat__step':
/home/sanduku/swarm/projects/floatspaceF/Boat.m:27: undefined
reference to `__objc_class_name_Agent2d'
make: *** [floatspace] Error 1


The offending lines of the code in Boat.m read:

          for (jamii=0; jamii < [[anchorSpace getBoatList] getCount];
jamii++){
            otherBoat = [[anchorSpace getBoatList] atOffset: jamii];
:line 27->   thatDist = [self getDistanceTo: otherBoat];
            if  ((int) thatDist){
              sumAnnoyance += [otherBoat getOffensiveness] * 
                [self getSensitivity] / thatDist;
              weightX += [otherBoat getXcoord] * [otherBoat
getOffensiveness];
              weightY += [otherBoat getYcoord] * [otherBoat
getOffensiveness];
              sumWeight += [otherBoat getOffensiveness];
    }

When I comment out the offending line, I get the same error message at
the next place in the code where a request is made to "otherBoat".

This code works fine when Boat is derived directly from a SwarmObject.
The message "undefined reference to '__objc_class_name_Agent2D'"
doesn't make sense to me.  Why would I get that if I have declared and
included Agent2D in the code?

Any help is appreciated


-- 
//////////////////////////////////////////////////
// Dr. Paul Box
// Dept of Geography and Earth Resources
// UMC 5240
// Utah State University      http://www.nr.usu.edu/~sanduku
// Logan, UT  84321           Phone: 435-797-2546
//////////////////////////////////////////////////

*  If Elvis was so great, why was he buried in the back yard like a
*  hamster?

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