MATLAB: Inability to clear object definition – nonfunctional “clear classes”

MATLABobject oriented programmingoop

I'm having an issues with a class that I've written. The class is a subclass of another class which is itself a handle class. Whenever I create an object of this class, the class definition becomes permanently loaded into Matlab and I can't clear it via any method that I can come up with other than restarting Matlab altogether. This means that if I change the class definition in a major way (adding a new method or changing the number of inputs or outputs of a method), I have to restart Matlab to use the changes.
The superclass that this class inherits does not appear to exhibit this behavior.
oo = CLASSNAME();
clear all
clear classes
The " clear classes " generates this warning:
Warning: Objects of 'CLASSNAME' class exist.  Cannot clear this class or any of its superclasses.
Then I make a new object:
oo = CLASSNAME();
Which, if I have modified the class definition, generates this warning:
Warning: The class file for 'CLASSNAME' has been changed, but the change cannot be applied because objects based
on the old class file still exist. If you use those objects, you might get unexpected results. You can use the
'clear' command to remove those objects. See 'help clear' for information on how to remove those objects.
Anyone seen anything like this before? Or have any idea what is going on? My hunch is that Matlab isn't destroying the object like it should because it thinks some variable is still referencing that object, but I don't have custom delete() methods defined for either class, so I don't know how I could have broken Matlab's object deletion.

Best Answer

Your hunch is correct!
clear() does not destroy the object, it only clears the handle to the object. This is the exact same as:
h = figure;
clear
The figure is still open but h is gone.
As long as the classes inherit from handle, they will have a factory delete method, make sure to delete them:
delete(h);
clear(h);
More
This can occur in R2012b if objects are saved in -v7.3 format files. When the file is read in, this warning will occur until a fresh session of MATLAB is started. Be sure to use -v7 when saving MAT files with objects in R2012b
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