在 iphone 应用程序上解析 JSON 对象和子元素

Question

我正在构建一个使用 UPC 数据库 API 的应用。我正在取回一个 JSON 对象，例如：http://www.simpleupc.com/api/methods/FetchNutritionFactsByUPC.php

{
"success":true,
"usedExternal":false,
"result"
    {
        "calories_per_serving":"150",
        "cholesterol_per_serving":"15",
        "cholesterol_uom":"Mg",
        "dvp_calcium":"30",
        "dvp_cholesterol":"4",
        "dvp_iron":"2",
        "dvp_protein":"17",
        "dvp_saturated_fat":"8",
        "dvp_sodium":"10",
        "dvp_total_fat":"4",
        "dvp_vitamin_a":"10","
        "dvp_vitamin_c":"0",
        "dvp_vitamin_d":"25",
        "fat_calories_per_serving":"25",
        "fiber_per_serving":"<1",
        "fiber_uom":"G",
        "ingredients":"Fat Free Milk, Milk, Sugar, Cocoa (Processed With Alkali),
                       Salt, Carrageenan, Vanillin (Artificial Flavor),
                       Lactase Enzyme, Vitamin A Palmitate And Vitamin D3.",
        "protein_per_serving":"8",
        "protein_uom":"G",
        "size":"240",
        "units":"mL",
        "servings_per_container":"8",
        "sodium_per_serving":"230",
        "sodium_uom":"Mg",
        "total_fat_per_serving":"2.5",
        "total_fat_uom":"G",
        "trans_fat_per_serving":"0",
        "trans_fat_uom":"G",
        "upc":"041383096013"
    }
}

我的问题是解析“ingredients”元素，它是对象字典的子列表。

您建议如何解析成分列表？如果我可以把它放到一个 NSArray 中，假设逗号是分隔符，那就太好了。

我试图这样做，但看起来它只是一个字符串，所以无法解析它。

任何建议都会受到欢迎。谢谢！

   //Thats the whole JSON object
    NSDictionary *json_dict = [theResponseString JSONValue];


   //Getting "results" which has all the product info
    NSArray *myArray = [[NSArray alloc] init];
     myArray = [json_dict valueForKey:@"result"];

现在我如何以数组形式从 myArray 中获取“成分”？

Answer 1

您将result 作为一个数组获取，但（在 JSON 术语中）它不是一个数组。 It's an object, so use an NSDictionary。像这样：¹

NSDictionary *result = [json_dict objectForKey:@"result"];

然后您可以从中获取内部ingredients 对象：

NSString *ingredients = [result objectForKey:@"ingredients"];

已根据@Bavarious 的评论编辑。

---

_{¹对于明显的错误，我深表歉意，因为我对 Objective-C 不是很精通。您可能需要为返回的NSDictionary 和NSString 指针分配内存；我不确定。}

Answer 2

这就是你需要做的所有事情：

 NSDictionary *json_dict = [theResponseString JSONValue];

 // Use a key path to access the nested element.
 NSArray *myArray = [json_dict valueForKeyPath:@"result.ingredients"];

编辑

哎呀，马特是对的。下面是处理字符串值的方法：

 // Use a key path to access the nested element.
 NSString *s = [json_dict valueForKeyPath:@"result.ingredients"];
 NSArray *ingredients = [s componentsSeparatedByString:@", "];

请注意，您可能需要修剪 '.'数组最后一个元素的字符。