NSInvalidArgumentException ...为什么？

Question

I have this code, where self.currentSet.imagesPrefix is a NSString and also [attributeDict objectForKey@"imagesPrefix"] is a NSSTring

self.currentSet.imagesPrefix=[attributeDict objectForKey:@"imagesPrefix"];

but in console I have this problem:

2011-11-15 16:04:08.850 MyApp[8579:707] -[__NSCFString setImagesPrefix:]: unrecognized selector sent to instance 0x168600
2011-11-15 16:04:08.857 MyApp[8579:707] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString setImagesPrefix:]: unrecognized selector sent to instance 0x168600'

Answer 1

我的猜测是您尚未合成imagesPrefix来生成setImagesPrefix方法。

Answer 2

This means that self.currentSet is not the object you think it is. Instead of chaining the properties, pull it apart into separate stages so you can debug:

id firstpart = self.currentSet;
NSLog(@"%@", firstpart);

This will reveal what self.currentSet really is. Prepare for a surprise. Then the real debugging can begin, because you'll have to figure out why it isn't what you think it is.