objective-c - NSMutableDictionary 中的编辑条目失败并出现错误：“无法识别的选择器已发送到实例”

Question

我有一个NSMutableDictionary这样初始化的：

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的内容：

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：

*** 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[__NSDictionaryI setObject:forKey:]: 无法识别的选择器发送到实例

我发现不知何故我的NSMutableDictionary一定已经变成了一个NSDictionary，这就是为什么我不能编辑它。也许您可以帮助我解决这个问题并为我指明正确的方向，或者向我展示我可以找到答案的资源？

Answer 1

您的“子词典”是不可变的。

尝试这个：

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