控制台提示
2013-07-11 00:50:43.232 SuperCalc[2816:c07] *** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFString characterAtIndex:]: Range or index out of bounds'
*** First throw call stack:
(0x1c92012 0x10cfe7e 0x1c91deb 0x1c58c0d 0x27ee 0x28f4 0x21f1 0x10e3705 0x172c0 0x17258 0xd8021 0xd857f 0xd76e8 0x46cef 0x46f02 0x24d4a 0x16698 0x1beddf9 0x1bedad0 0x1c07bf5 0x1c07962 0x1c38bb6 0x1c37f44 0x1c37e1b 0x1bec7e3 0x1bec668 0x13ffc 0x1cad 0x1bd5 0x1)
libc++abi.dylib: terminate called throwing an exception
