Sorting core data position changes with sort descriptors for iPhone?

Try this, assuming your positionChange is an NSNumber.

The reason that code fails with the unsupported NSSortDescriptor selector error is that you're using a SQLite data store and attempting to use a Cocoa method as the sort descriptor. With a SQLite store, sort descriptors are translated on the fly into SQL and sorting is done by SQLite. That really helps performance but it also means that sorting is done in a non-Cocoa environment where your custom comparison method doesn't exist.

Sorting like this only works for common, known methods and not for arbitrary Cocoa code.

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