objective-c - NSMutableDictionary 中的编辑条目失败，错误为 : "unrecognized selector sent to instance"

Question

我有一个NSMutableDictionary初始化如下:

dictionary = [NSMutableDictionary dictionaryWithDictionary:@{
    @"0": @{
        @"title": @"Description",
        @"value": @"Enter Description",
    },
    @"1": @{
        @"title": @"Amount",
        @"value": @"Enter Amount",
    }
}];

现在我想修改@"Enter Description"我一直在尝试这样做:

NSMutableDictionary *tempDictionary = [dictionary objectForKey:@"0"];
[tempDictionary setObject:@"TEST" forKey:@"value"];
//The next line doesn't get executed yet since the error occurs at the line above.
//So Maybe there is something wrong with the one below as well ;-)
[dictionary setObject:tempDictionary forKey:@"0"];

但是我收到以下错误消息:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance

我发现不知何故我的NSMutableDictionary一定已经变成了NSDictionary ，这就是为什么我无法编辑它。也许您可以帮我解决这个问题，并为我指明正确的方向，或者向我展示可以找到答案的资源？

Answer 1

您的“子词典”是不可变的。

试试这个:

dictionary = [NSMutableDictionary dictionaryWithDictionary:@{
                                                             @"0": [NSMutableDictionary dictionaryWithDictionary:@{
                                                                     @"title": @"Description",
                                                                     @"value": @"Enter Description",
                                                                     }],
                                                             @"1": [NSMutableDictionary dictionaryWithDictionary:@{
                                                                     @"title": @"Amount",
                                                                     @"value": @"Enter Amount",
                                                                     }]
                                                             }];