我可以像这样设置UITextView的标签：
_textView.tag = 5;
但是，当我使用变量时，程序会崩溃并显示下面给出的错误消息。
_textView.tag = rowNumber;
有趣的是，在进行上述分配时，程序不会崩溃，但稍后会发生。
这是什么原因？是否不允许在运行时更改标签？
错误讯息：
-[UITextView configureForRow:mainTitle:mainTitleColor:subtitle:subtitleColor:backgroundColor:objectWithTargetMethod:]: unrecognized selector sent to instance 0x12ed26550
2014-04-17 14:18:54.600 Loggilyze[8153:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITextView configureForRow:mainTitle:mainTitleColor:subtitle:subtitleColor:backgroundColor:objectWithTargetMethod:]: unrecognized selector sent to instance 0x12ed26550'
*** First throw call stack:
(0x18473a950 0x190c401fc 0x18473f604 0x18473d330 0x18465d08c 0x100077618 0x18784c904 0x1877eae64 0x1877ea62c 0x1876feff8 0x1872f0258 0x1872eae20 0x1872eacd8 0x1872ea560 0x1872ea304 0x1872e3c38 0x1846fb0a8 0x1846f8330 0x1846f86bc 0x1846396d0 0x18a31dc0c 0x18776afdc 0x100012b44 0x191233aa0)
libc++abi.dylib: terminating with uncaught exception of type NSException