I gets crash:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to delete item 20 from section 0 which only contains 20 items before the update'
My changes:
First Changes
insert(0), insert(1), insert(2), insert(3), insert(4), insert(5), insert(6), insert(7), insert(8), insert(9), insert(10), insert(11), insert(12), insert(13), insert(14), insert(15), insert(16), insert(17), insert(18), insert(19)
Second Changes
insert(0), insert(1), insert(2), insert(3), insert(4), insert(5), insert(6), insert(7), insert(8), insert(9), insert(10), insert(11), insert(12), insert(13), insert(14), insert(15), insert(16), insert(17), insert(18), insert(19), update(20(was 0))
Crash!
I think changes update(20) should be update(0). Maybe collection view sees the changed items before inserted