objective-c - objective-c : updating values for key for an NSMutableDictionary?

Question

我有一个 NSMutableDictionary，其中包含最初设置的键和值。后来我需要更新某些键的值，我想我只需要这样做[mutableDict setValue:val forKey:key]，但这会引发异常:

[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object

我做错了什么？(我在可变字典的每个键内都有另一个可变字典，但我不认为这就是原因)

Answer 1

如果您想保持 100% 接受，我会复制粘贴我的评论

保罗.s

For some reason you are actually working with an NSDictionary not an NSMutableDictionary. Hard to say why without more code, maybe you are using a copy obtained by calling copy or you have loaded the dictionary from a plist/userDefaults.. Can we see some more code?

丹尼斯

@Paul.s Yes, I did copy an NSMutableDictionary. Would that be why? If it is, then what else should I use to copy?

保罗.s

Use mutableCopy instead of copy to get a mutable dictionary

丹尼斯

@Paul.s oh.. didn't know about that. I'm new to Objective-C and I tried to search for what I am doing wrong but I missed it :( Thank you!!