*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ViewController copyWithZone:]: unrecognized selector sent to instance 0x12dd08ef0'
*** First throw call stack:
(0x1854ca084 0x195ab00e4 0x1854d1094 0x1854cde48 0x1853d308c 0x195ac0b94 0x10008d760 0x10008c410 0x189c812f4 0x189c6a44c 0x189c80c90 0x189c8091c 0x189c79e70 0x189c4d660 0x189eebd6c 0x189c4bbc8 0x185482324 0x1854815c8 0x18547f678 0x1853ad664 0x18e4ef5a4 0x189cb2984 0x10008d8a0 0x19611ea08)
libc++abi.dylib: terminating with uncaught exception of type NSException
代理的类型如果不是weak会报上述错误,代理应为弱引用。