unrecognized selector sent to instance 0x10b34e810

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A mistake ：

*** Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘-[NSURLError isEqualToString:]: unrecognized selector sent to instance 0x10b34e810’ *** First throw call stack:

(lldb) po 0x10b34e810 Error Domain=NSURLErrorDomain Code=-1004 “Could not connect to the server.” UserInfo=0x10a582670 {NSUnderlyingError=0x10a664e90 “Could not connect to the server.”, NSErrorFailingURLStringKey= , NSLocalizedDescription=Could not connect to the server.}

Print the 0x10b34e810 object , doubt NSError *error Forced to string Type of unsuccessful

Hang up here .

..

(lldb) po (NSString*)error Error Domain=NSURLErrorDomain Code=-1004 “Could not connect to the server.” UserInfo=0x10a5223a0 {NSUnderlyingError=0x10b181140 “Could not connect to the server.”, NSErrorFailingURLStringKey=, NSLocalizedDescription=Could not connect to the server.}

summary ： The basic type of value can be converted ,nsobject Type cannot be forcibly converted （ General basic types can be forcibly converted .

int,float Can turn into string .

Can object types not be converted ..

example nsurl Cannot be converted into string..nserror Nor can it be converted into string） What a major common sense , And always forget .

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