帮助解析嵌套的 JSON 对象答案

【问题标题】：Help parsing a nested JSON object帮助解析嵌套的 JSON 对象
【发布时间】：2011-07-05 00:28:19
【问题描述】：

我有以下 JSON：

{
    "meta": {
        "code": 200
    }, 
    "response": {
        "deals": [
            {
                "id": 32373, 
                "date_added": "2011-01-13 12:12:50", 
                "end_date": "2011-01-14 10:00:00", 
                "active": 1, 
                "discount": {
                    "raw": 71, 
                    "formatted": "71%"
                }, 
                "price": {
                    "raw": "85.00", 
                    "formatted": "$85"
                }, 
                "value": {
                    "raw": "300.00", 
                    "formatted": "$300"
                }, 
                "purchased": 82, 
                "left": null, 
                "title": "$85 For $300 Babyface Facial At Park Avenue MedSpa", 
                "yipit_title": "71% off Babyface Facial", 
                "url": "http://yipit.com/aff/click/?deal=AvwTADtE&key=F374EFbM", 
                "yipit_url": "http://yipit.com/new-york/livingsocial/85-for-300-babyface-facial-at-park-avenue-medspa/", 
                "images": {
                    "image_big": "http://d22nv2k05ynu7x.cloudfront.net/deal_images/deal/85-for-300-babyface-facial-at-park-avenue-medspa-1294920769_display_image.jpg", 
                    "image_small": "http://d22nv2k05ynu7x.cloudfront.net/deal_images/deal/85-for-300-babyface-facial-at-park-avenue-medspa-1294920769_small_image.jpg"
                }, 
                "division": {
                    "slug": "new-york", 
                    "name": "New York", 
                    "active": 1, 
                    "time_zone_diff": -4, 
                    "lat": "40.7142690000000000", 
                    "lon": "-74.0059730000000000", 
                    "url": "http://yipit.com/new-york/"
                }, 
                "tags": [
                    {
                        "name": "Facial", 
                        "slug": "facial", 
                        "url": "http://yipit.com/new-york/deals/facial/"
                    }, 
                    {
                        "name": "Spa", 
                        "slug": "spa", 
                        "url": "http://yipit.com/new-york/deals/spa/"
                    }
                ], 
                "business": {
                    "name": "Park Avenue MedSpa", 
                    "url": "", 
                    "locations": [
                        {
                            "address": "565 Park Ave", 
                           "locality": "New York",
                            "phone": "212-593-8821", 
                            "lat": null, 
                            "lon": null
                        }
                    ]
                }, 
                "source": {
                    "name": "LivingSocial", 
                    "slug": "livingsocial", 
                    "paid": 0, 
                    "url": "http://yipit.com/new-york/livingsocial"
                }
            }
        ]
    }
}

这是我的解析方式：

    NSArray *deals = [[results objectForKey:@"response"] valueForKey:@"deals"];
    NSLog(@"%@",[[results objectForKey:@"response"] valueForKey:@"deals"]);

    for(NSDictionary* deal in deals)
    {
        NSLog(@"Title: %@", [deal valueForKey:@"title"]);
        NSLog(@"URL: %@", [deal valueForKey:@"url"]);
        NSLog(@"Value: %@", [[deal valueForKey:@"value"] valueForKey:@"formatted"]);
        NSLog(@"Picture URL: %@", [[deal valueForKey:@"images"] valueForKey:@"image_small"]);
        NSLog(@"Business: %@", [[deal valueForKey:@"business"] valueForKey:@"name"]);
        NSLog(@"Address: %@", [[[deal valueForKey:@"business"] valueForKey:@"locations"] valueForKey:@"address"]);
        NSLog(@"City: %@", [[[deal valueForKey:@"business"] valueForKey:@"locations"] valueForKey:@"locality"]);
        NSLog(@"Phone: %@", [[[deal valueForKey:@"business"] valueForKey:@"locations"] valueForKey:@"phone"]);

        [items addObject:deal];
    }

我的日志记录看起来不错，除了 Address、City 和 Phone。这是日志：

Title: $10 for $20 Worth of Food and Drinks at Blondies in Tempe
URL: http://yipit.com/aff/click/?deal=cHBPNZ3w&key=93HU7t2d
Value: $20
Picture URL: http://d22nv2k05ynu7x.cloudfront.net/deal_images/deal/50-off-at-blondies-sports-bar-1298454745_small_image.jpg
Business: Blondies Sports Bar
Address: (
    "501 S Mill Ave"
)
City: (
    Tempe
)
Phone: (
    "702-737-0444"
)

【问题讨论】：

根据您提供的 JSON，locations 是一个数组，因此从 valueForKey: 返回的值包含在 NSArray 实例中（因此有括号）。

标签： iphone objective-c cocoa-touch json nsdictionary

【解决方案1】：

根据您提供的 JSON，locations 是一个数组（这就是方括号的含义），因此从 valueForKey: 返回的值包含在 NSArray 实例中（因此是括号）。

您可以在最后一次调用valueForKey: 之前使用objectAtIndex: 来获取您正在寻找的值。

顺便说一句，你也可以使用valueForKeyPath:来简化访问嵌套值，例如

[deal valueForKeyPath:@"business.name"];

【讨论】：

感谢您的澄清。我对 valueForKeyPath 感兴趣，我不知道。我尝试了您的以下 sn-p，但它返回 null。你能编辑你的答案以显示完整的代码吗？
上例中对valueToKeyPath: 的调用可以替代像这样的表达式（来自您发布的代码）[[deal valueForKey:@"business"] valueForKey:@"name"]，其含义基本相同。

【解决方案2】：

您可以尝试将代码更改为以下内容：

NSDictionary *primaryLocation =  [[[deal valueForKey:@"business"] valueForKey:@"locations"] objectAtIndex:0];
NSLog(@"Address: %@", [primaryLocation valueForKey:@"address"]);
NSLog(@"City: %@", [primaryLocation valueForKey:@"locality"]);
NSLog(@"Phone: %@", [primaryLocation valueForKey:@"phone"]);

【讨论】：

【解决方案3】：

[[deal valueForKey:@"business"] valueForKey:@"locations"] 返回一个数组。在 NSArray 上调用 -valueForKey: 会为数组中的每个对象执行 valueForKey: 并返回结果数组（请参阅 NSArray 文档）。这就是你得到的，对应值的数组。

【讨论】：

还是有点困惑，能不能告诉我如何从返回的 NSArray 中取出那个值？
使用objectAtIndex: 获取数组中的一项。