我在堆栈跟踪中遇到NSCFNumber和UILabel drawTextInRect：无法识别的选择器错误。这就是堆栈跟踪的样子：
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber length]: unrecognized selector sent to instance 0xad5a260'
*** First throw call stack:
(
0 CoreFoundation 0x01f039e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x01c838e5 objc_exception_throw + 44
2 CoreFoundation 0x01fa0a43 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x01ef3d0b ___forwarding___ + 1019
4 CoreFoundation 0x01ef38ee _CF_forwarding_prep_0 + 14
5 UIKit 0x00b02773 -[UILabel _shadow] + 45
6 UIKit 0x00b03bd2 -[UILabel drawTextInRect:] + 70
7 UIKit 0x00b0610c -[UILabel drawRect:] + 98
8 UIKit 0x009b4893 -[UIView(CALayerDelegate) drawLayer:inContext:] + 504
9 QuartzCore 0x0060db39 -[CALayer drawInContext:] + 123
10 QuartzCore 0x0060da6a _ZL16backing_callbackP9CGContextPv + 96
11 QuartzCore 0x004fbf3c CABackingStoreUpdate_ + 2656
12 QuartzCore 0x0060da02 ___ZN2CA5Layer8display_Ev_block_invoke + 93
13 QuartzCore 0x00641ee3 x_blame_allocations + 15
14 QuartzCore 0x0060d86d _ZN2CA5Layer8display_Ev + 1519
15 QuartzCore 0x0060dab9 -[CALayer _display] + 33
16 QuartzCore 0x0060d276 _ZN2CA5Layer7displayEv + 144
17 QuartzCore 0x0060da93 -[CALayer display] + 33
18 QuartzCore 0x00601c43 _ZN2CA5Layer17display_if_neededEPNS_11TransactionE + 323
19 QuartzCore 0x00601cbc _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 38
20 QuartzCore 0x005683ee _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
21 QuartzCore 0x00569779 _ZN2CA11Transaction6commitEv + 393
22 QuartzCore 0x00569e4c _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 92
23 CoreFoundation 0x01ecbb6e __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
24 CoreFoundation 0x01ecbabf __CFRunLoopDoObservers + 399
25 CoreFoundation 0x01ea9a54 __CFRunLoopRun + 1076
26 CoreFoundation 0x01ea91d3 CFRunLoopRunSpecific + 467
27 CoreFoundation 0x01ea8feb CFRunLoopRunInMode + 123
28 GraphicsServices 0x03d1c5ee GSEventRunModal + 192
29 GraphicsServices 0x03d1c42b GSEventRun + 104
30 UIKit 0x009463db UIApplicationMain + 1225
31 PocketCTF 0x00026e8d main + 141
32 libdyld.dylib 0x02881725 start + 0
)
我不确定哪条线导致此错误，因为Xcode只是断点到主运行循环。我已经尝试使用异常和符号断点来查看导致问题的行但没有用。我有什么办法可以找到造成这种情况的线路吗？
答案 0 :(得分：2)
经过几个小时的调试，当然我在这里发帖后找到解决方案..我试图根据NSDictionary值设置文本，如此，
[label setText:[json objectForKey:@"text"]];
但UILabel不是id，而是NSString（正如@danielbeard所指出的那样）
[label setText:[[json objectForKey:@"text"] stringValue]];