用了 placehoder的功能 pop 时报错

[realSummer]

2017-07-18 09:58:49.211 JiDing[1213:105514] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x7fd88b905200 of class UITextView was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x600000420f00> (
<NSKeyValueObservance 0x600000253e90: Observer: 0x7fd88b905200, Key path: frame, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x600000253ec0>
<NSKeyValueObservance 0x600000254040: Observer: 0x7fd88b905200, Key path: bounds, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x600000254070>
<NSKeyValueObservance 0x600000254130: Observer: 0x7fd88b905200, Key path: font, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x600000254160>
<NSKeyValueObservance 0x600000253f80: Observer: 0x7fd88b905200, Key path: text, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x600000254220>
<NSKeyValueObservance 0x600000254190: Observer: 0x7fd88b905200, Key path: textAlignment, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x6000002542e0>
<NSKeyValueObservance 0x600000254250: Observer: 0x7fd88b905200, Key path: textContainerInset, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x600000254400>
)'