按照这样做好demo后，每次切换textview的时候都会终止运行，不知道是什么原因
返回信息如下：
2016-01-12 00:54:28.935 UITestingDemo[2736:109250] -[ViewController userName:]: unrecognized selector sent to instance 0x7fc7ba49b500
2016-01-12 00:54:28.940 UITestingDemo[2736:109250] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ViewController userName:]: unrecognized selector sent to instance 0x7fc7ba49b500'
*** First throw call stack:
(
0 CoreFoundation 0x000000010bc30885 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x000000010b6a9df1 objc_exception_throw + 48
2 CoreFoundation 0x000000010bc38b5d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000010bb85e3a ___forwarding___ + 970
4 CoreFoundation 0x000000010bb859e8 _CF_forwarding_prep_0 + 120
5 UIKit 0x000000010bfda257 -[UIApplication sendAction:to:from:forEvent:] + 125
6 UIKit 0x000000010bfda1b2 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 79
7 UIKit 0x000000010c135422 -[UIControl sendAction:to:forEvent:] + 67
8 UIKit 0x000000010c1356c6 -[UIControl _sendActionsForEvents:withEvent:] + 272
9 UIKit 0x000000010c8f2fb9 -[UITextField _resignFirstResponder] + 299
10 UIKit 0x000000010c1c8ffb -[UIResponder _finishResignFirstResponder] + 234
11 UIKit 0x000000010c8f2de2 -[UITextField _finishResignFirstResponder] + 49
12 UIKit 0x000000010c1c90b4 -[UIResponder resignFirstResponder] + 137
13 UIKit 0x000000010c8f2caf -[UITextField resignFirstResponder] + 136
14 UIKit 0x000000010c1c8d80 -[UIResponder becomeFirstResponder] + 366
15 UIKit 0x000000010c07318e -[UIView(Hierarchy) becomeFirstResponder] + 138
16 UIKit 0x000000010c8f1c5a -[UITextField becomeFirstResponder] + 51
17 UIKit 0x000000010c47a003 -[UITextInteractionAssistant(UITextInteractionAssistant_Internal) setFirstResponderIfNecessary] + 287
18 UIKit 0x000000010c47d997 -[UITextInteractionAssistant(UITextInteractionAssistant_Internal) oneFingerTap:] + 3817
19 UIKit 0x000000010c474447 _UIGestureRecognizerSendTargetActions + 153
20 UIKit 0x000000010c46ed7e _UIGestureRecognizerSendActions + 162
21 UIKit 0x000000010c46d577 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 611
22 UIKit 0x000000010c473962 ___UIGestureRecognizerUpdate_block_invoke720 + 79
23 UIKit 0x000000010c4737ec _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 342
24 UIKit 0x000000010c466aaf _UIGestureRecognizerUpdate + 2759
25 UIKit 0x000000010c0406d7 -[UIWindow _sendGesturesForEvent:] + 1137
26 UIKit 0x000000010c0417c6 -[UIWindow sendEvent:] + 849
27 UIKit 0x000000010bff6705 -[UIApplication sendEvent:] + 263
28 UIKit 0x000000010bfd35df _UIApplicationHandleEventQueue + 6031
29 CoreFoundation 0x000000010bb5b0f1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
30 CoreFoundation 0x000000010bb50eac __CFRunLoopDoSources0 + 556
31 CoreFoundation 0x000000010bb50363 __CFRunLoopRun + 867
32 CoreFoundation 0x000000010bb4fd78 CFRunLoopRunSpecific + 488
33 GraphicsServices 0x000000010f1eebca GraphicsServices + 52170
34 UIKit 0x000000010bfd879b UIApplicationMain + 171
35 UITestingDemo 0x000000010b1b0adf main + 111
36 libdyld.dylib 0x000000010e19fa05 libdyld.dylib + 10757
37 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
