kvc error

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x7fb3ddd0ba80 of class BtnViewController was deallocated while key value observers were still registered with it.

被关注的对象的生命周期不足！

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原文地址：https://www.cnblogs.com/code-Officer/p/6305445.html