一直以来两个都用，但是没有区分过，基本都是处理字符串。今天整理下异同，以后写代码也能开拓思路，优化算法。 1、setValue /* Send -setObject:forKey: to the receiver, unless the value is nil, in which case send -removeObjectForKey:.*/- (void)setValue:(nul

-[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object' 解决方法： 错误：NSMutableDictionary*d =[[[NSUserDefaults standardUserDefaults] objectForKey:@"xxxx"] mutableCopy]; 修改：NS

1 setValue： forKey：的定义 @interface NSMutableDictionary(NSKeyValueCoding) /* Send -setObject:forKey: to the receiver, unless the value is nil, in which case send -removeObject:forKey:. */ - (voi