Avoiding runtime errors with CustomProbeMap

[Benedikt Stefansson]

Hi,

This is a brief note on errors that may arise when you port an app to
1.0.5. Initially when I ported one of my sims to 1.0.5 I got the
following error messages for innocuous code that simply creates the
custom probe map for my ModelSwarm:

ModelSwarm.m: In function `_c_ModelSwarm__createBegin_':
ModelSwarm.m:35: warning: `CustomProbeMap' does not respond to
`setProbedClass:'
...<ton of warning deleted>
ModelSwarm.m:73: warning: `CustomProbeMap' does not respond to
`addProbe:'
ModelSwarm.m:76: warning: `CustomProbeMap' does not respond to
`addProbe:'

Although these were only warnings, the runtime would complain and refuse
to create a custom probe map for the ModelSwarm and pull up the default
(full) map instead in the GUI.

After fooling around with different things, casting variables
differently, using a ProbeMap instance instead of CustomProbeMap etc., I
finally realized that all that needed to be done was to change the
following line:

+createBegin: (id) aZone {
  ModelSwarm * obj;
  CustomProbeMap * probeMap; <---- THIS CAUSES THE WARNING

The solution is to define the variable in terms of the protocol,
CustomProbeMap, instead of using static typing:

+createBegin: (id) aZone {
  ModelSwarm * obj;
  id <CustomProbeMap> probeMap; <---- EVERYBODY HAPPY

Here is a shortened version of the +createBegin: method, for the record:

+createBegin: (id) aZone {
  ModelSwarm * obj;
  id <CustomProbeMap> probeMap;

  // First, call our superclass createBegin
  obj = [super createBegin: aZone];

  obj->alpha=168.0;
  obj->beta=0.667;
  ... <ton of instance variable declarations deleted>
  obj->starting=9;

  probeMap = [CustomProbeMap createBegin: aZone];
  [probeMap setProbedClass: [self class]];
  probeMap = [probeMap createEnd];

  // Add in a bunch of variables, one per simulation parameter
  [probeMap addProbe: [probeLibrary getProbeForVariable: "alpha"
        inClass: [self class]]];
  [probeMap addProbe: [probeLibrary getProbeForVariable: "beta"
        inClass: [self class]]];
  ...<ton of probe declarations deleted>
  [probeMap addProbe: [probeLibrary getProbeForVariable:
"startingPrice1"
        inClass: [self class]]];

  [probeLibrary setProbeMap: probeMap For: [self class]];

  return obj;
}

-Benedikt

--
----------------
Benedikt Stefansson                 address@hidden
Department of Economics, UCLA       Fax. (310) 825-9528
Los Angeles, CA 90095-1477          Tel. (310) 825-1777




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