However, it would be nice to have a unified model for overriding and I can see this tripping a lot of people up, especially if they try to override internal ext classes to work around problems. I ran into it trying to alter TableChunker to let me select text in a grid.
Thanks for the info - I'll assume this is expected behavior, then.
I understand how it's working now - setting the object property rather than touching the prototype was what my last snippet did. However, it seemed to me with the new Ext.define syntax you tried to present a unified way to create the definition for classes, both instantiable and ones intended to be singletons. Creating one intended to be singleton just requires a different config attribute. Given this, it seemed counterintuitive to me that the override mechanism wasn't smart enough to figure out what I meant when I tried to override a method on a singleton - it seemed there was a disconnect between define and override.
This tripped me up because just looking at TableChunker it looked like a regular class. Not a huge deal either way; we'll just have to condition ourselves to look for the singleton config option.