Question

我为UiTableView的每个单元格获取以下NSDictionary。我必须能够在下面的资产子结构中向下钻取并获得第一个id值。

{
    assets =     (
                {
            "chunk_size" = 262144;
            file =             {
                "is_dirty" = 0;
                "mongo_grid_f_s_file" =                 {
                    file =                     {
                        "_id" =                         {
                            "$id" = 503a58e09b41648f69000001;
                        };
                        chunkSize = 262144;
                        filename = "/private/var/tmp/phpPPZsUf";
                        length = 5849;
                        md5 = 5f2700f4d953ef866fe1d4967f9965fb;
                        name = Image1;
                        uploadDate =                         {
                            sec = 1346001120;
                            usec = 819000;
                        };
                    };
                    gridfs =                     {
                        chunks =                         {
                            w = 1;
                            wtimeout = 10000;
                        };
                        "chunks_name" = "assets.chunks";
                        "files_name" = "assets.files";
                        w = 1;
                        wtimeout = 10000;
                    };
                };
            };
            id = 503a58e09b41648f69000001;
            length = 5849;
            md5 = 5f2700f4d953ef866fe1d4967f9965fb;
            name = Image1;
            "upload_date" = "0.81900000 1346001120";
        },
                {
            "chunk_size" = 262144;
            file =             {
                "is_dirty" = 0;
                "mongo_grid_f_s_file" =                 {
                    file =                     {
                        "_id" =                         {
                            "$id" = 503a58e09b41648f69000004;
                        };
                        chunkSize = 262144;
                        filename = "/private/var/tmp/phphxvI3H";
                        length = 1551;
                        md5 = f193ffe87eb0138608a206dcf72bf704;
                        name = Image2;
                        uploadDate =                         {
                            sec = 1346001120;
                            usec = 841000;
                        };
                    };
                    gridfs =                     {
                        chunks =                         {
                            w = 1;
                            wtimeout = 10000;
                        };
                        "chunks_name" = "assets.chunks";
                        "files_name" = "assets.files";
                        w = 1;
                        wtimeout = 10000;
                    };
                };
            };
            id = 503a58e09b41648f69000004;
            length = 1551;
            md5 = f193ffe87eb0138608a206dcf72bf704;
            name = Image2;
            "upload_date" = "0.84100000 1346001120";
        }
    );
    coordinates =     {
        latitude = "37.78584";
        longitude = "-122.4064";
    };
    "created_at" = "2012-08-26T12:12:00-0500";
    id = 503a58e09b4164cf5a00000a;
    "number_of_cars" = 1;

}

我尝试了以下内容：

 NSDictionary * classifiedAssets = [classified objectForKey:@"assets"];

然后为了获得每个id，我已经完成了：

[classifiedImages objectForKey:@"id"]

但我得到的只是：

(503a58e09b41648f69000001, 503a58e09b41648f69000004)

我希望找回各种ID的NSArray而不是括号逗号分隔列表。

任何提示？

Answer 1

我想你可能已经拥有了你需要的东西;这是解释：

NSDictionary * classifiedAssets = [classified objectForKey:@"assets"];

不完全是你所期望的：你可能认为它是一个NSDictionary（由于你输入了变量），但它实际上是一个NSArray（由于JSON中的括号而不是大括号）。然后这个：

[classifiedImages objectForKey:@"id"]
// by which I *assume* you mean:
[classifiedAssets valueForKey:@"id"]

实际上正在利用NSArrays的一个漂亮功能：在NSArray上调用valueForKey:会为您提供一个NSArray，其中包含对每个成员调用valueForKey:的结果。

我假设你在谈论NSLog系列中的parens和逗号。在该上下文中，用括号包围的以逗号分隔的一组事物表示 NSArray（尝试记录它的class并查看）

Answer 2

要获得一系列资产ID，您可以执行以下操作：

// Assuming that 'classified' is the dictionary you have posted
NSArray *ids = [classified valueForKeyPath:@"assets.id"];

现在，valueForKeyPath的有趣之处在于，如果遇到valueForKey

，让我们在为每个对象调用NSArray的同时通过点表示法向下钻取对象

如何在下面的NSDictionary中深入研究？

2 个答案: