iOS Development--Exception: [__nscfnumber length]: Unrecognized selector sent to instance

Terminating app due to uncaught exception ' nsinvalidargumentexception ', Reason: '-[__nscfnumber length]: Unrecognized Selector sent to instance

The case of others on the internet is exactly the same as mine, so I stole his pictures and articles directly.

Http://www.tuicool.com/articles/EZ3uMb7

This error is the comments data type of the author parsing the field in the Pilst file is the NSNumber type, and the NSString type is written when the dictionary goes to the model, so the above error is reported;

Workaround:
Change the comments in the model property to the NSNumber type, and do the data conversion when you drop it.
Set Property type to NSNumber
When invoking the data type conversion, turn into nsstring can be

iOS Development--Exception: [__nscfnumber length]: Unrecognized selector sent to instance