使用FMDB解析JSON，返回NSCFString而不是NSDictionary

Question

我使用resultDictionary来获取存储在数据库中的json数据。

当我尝试解析字典时，调试部分会告诉我这个[__NSCFString objectForKeyedSubscript：]

FMResultSet *resultSet = [db executeQuery:@"SELECT json FROM cacheinfo"];
while ([resultSet next]) {
dicDbResource = resultSet.resultDictionary;
results = dicDbResource[@"json"];
NSLog(@"bannerbooks:%@",results[@"BannerBooks"]);
}

结果打印如下：

    results:{
    BannerBooks =     (
                {
            BannerIMGURL = "qqq";
            BannerLink = "qqq";
            linkISBN = "<null>";
        },
                {
            BannerIMGURL = "qqq";
            BannerLink = "qqq";
            linkISBN = "<null>";
        },
                {
            BannerIMGURL = "qqq";
            BannerLink = "qqq";
            linkISBN = "<null>";
        },
    )
}