从可变字典中删除对象会引发异常

Question

尝试从NSMutableDictionary中删除对象后,我收到异常.相关代码如下.'settings'被传递给方法,可以是NSDictionary或NSMutableDictionary.

 NSMutableDictionary *mutableSettings = nil;
 if ([settings isKindOfClass:[NSMutableDictionary class]])
     mutableSettings = (NSMutableDictionary *)settings;
 else 
     mutableSettings = [[[NSMutableDictionary alloc] initWithDictionary:settings] autorelease];

 [mutableSettings removeObjectForKey:@"akey"];

这与崩溃

*由于未捕获的异常'NSInternalInconsistencyException'终止应用程序,原因:' - [__ NSCFDictionary removeObjectForKey:]:发送到immutable对象的mutating方法'

这有什么不对吗？谢谢.

Answer 1

这里的问题是,由于它是一个类集群,因此它们都返回NSDictionary并NSMutableDictionary返回.__NSCFDictionaryclassNSDictionary

我想你只需要制作一本可变的settings字典副本,无论它是否可变.

NSMutableDictionary *mutableSettings = [settings mutableCopy];