'setObjectForKey：key不能为nil'异常，如何判断哪一个

Question

我的应用程序是随机的（有时它确实，有时它不会）崩溃：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** setObjectForKey: key cannot be nil'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010988ec65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010b63bbb7 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000109793af8 -[__NSDictionaryM setObject:forKey:] + 968
    3   MultipeerConnectivity               0x00000001096e32e2 -[MCNearbyServiceBrowser netServiceBrowser:didFindService:moreComing:] + 251
    4   CFNetwork                           0x000000010c2ca2dd -[NSNetServiceBrowser _dispatchCallBack:flags:error:] + 968
    5   CFNetwork                           0x000000010c217fe2 _ZL14_BrowserCancelP21__CFNetServiceBrowser + 133
    6   CoreFoundation                      0x00000001097c2431 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    7   CoreFoundation                      0x00000001097b82fd __CFRunLoopDoSources0 + 269
    8   CoreFoundation                      0x00000001097b7934 __CFRunLoopRun + 868
    9   CoreFoundation                      0x00000001097b7366 CFRunLoopRunSpecific + 470
    10  GraphicsServices                    0x000000010d1a3a3e GSEventRunModal + 161
    11  UIKit                               0x000000010a36f8c0 UIApplicationMain + 1282
    12  MyApp                               0x0000000109099137 main + 135
    13  libdyld.dylib                       0x000000010cccc145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

如何在Xcode中告诉哪一行代码或集合对象导致问题？

更新

我做了回答和评论建议，并在命令中添加了断点，现在，在错误之前，我得到了这个：

  

*** setObjectForKey：key不能为nil

     

4354859399

     

3534170

     

140567501647968

     

140567492355160

     

140567492355168

     

4354751672

     

4294967279

我仍然不知道这意味着什么...

Answer 1

在Xcode的左侧面板中，转到“断点”标签，单击+按钮并添加Exception Breakpoint。它将捕获任何异常并告诉您它们发生的位置。