如何使用Codable

时间：2017-12-29 09:50:59

标签： json swift codable

我需要帮助从服务器解析JSON。这是JSON：

{
"response": {
    "items": [
        {
            "type": "post",
            "source_id": -17507435,
            "date": 1514538602,
            "post_id": 4105,
            "post_type": "post",
            "text": "Some text here",
            "marked_as_ads": 0,
            "attachments": [
                {
                    "type": "photo",
                    "photo": {
                        "id": 456239655,
                        "album_id": -7,
                        "owner_id": -17507435,
                        "user_id": 100,
                        "photo_75": "https://sun1-3.userapi.com/c840632/v840632924/3b7e7/4YUS7DlaLK8.jpg",
                        "photo_130": "https://sun1-3.userapi.com/c840632/v840632924/3b7e8/Ffpb4ZUlulI.jpg",
                        "photo_604": "https://sun1-3.userapi.com/c840632/v840632924/3b7e9/-pkl6Qdb9hk.jpg",
                        "width": 439,
                        "height": 312,
                        "text": "",
                        "date": 1514538602,
                        "post_id": 4105,
                        "access_key": "6a61a49570efd9c39c"
                    }
                }
            ],
            "post_source": {
                "type": "api"
            },
            "comments": {
                "count": 0,
                "groups_can_post": true,
                "can_post": 1
            },
            "likes": {
                "count": 0,
                "user_likes": 0,
                "can_like": 1,
                "can_publish": 1
            },
            "reposts": {
                "count": 0,
                "user_reposted": 0
            },
            "views": {
                "count": 2
            }
        }
    ],
    "profiles": [],
    "groups": [
        {
            "id": 17507435,
            "name": "Literature Museum",
            "screen_name": "samlitmus",
            "is_closed": 0,
            "type": "group",
            "is_admin": 0,
            "is_member": 1,
            "photo_50": "https://pp.userapi.com/c615722/v615722068/e58c/d5Y8E_5689s.jpg",
            "photo_100": "https://pp.userapi.com/c615722/v615722068/e58b/Hm05ga3x2J8.jpg",
            "photo_200": "https://pp.userapi.com/c615722/v615722068/e589/yoG_DDalFII.jpg"
        },
        {
            "id": 27711883,
            "name": "E:\\music\\melodic hardcore",
            "screen_name": "e_melodic_hc",
            "is_closed": 0,
            "type": "page",
            "is_admin": 0,
            "is_member": 1,
            "photo_50": "https://pp.userapi.com/c628220/v628220426/47092/xepNnC7pSBw.jpg",
            "photo_100": "https://pp.userapi.com/c628220/v628220426/47091/uAokr-c3NQ8.jpg",
            "photo_200": "https://pp.userapi.com/c628220/v628220426/4708f/eNY4vzooz4E.jpg"
        },
        {
            "id": 81574241,
            "name": "DOS4GW.EXE",
            "screen_name": "dos4gw",
            "is_closed": 0,
            "type": "page",
            "is_admin": 0,
            "is_member": 1,
            "photo_50": "https://pp.userapi.com/c622118/v622118651/e045/vlhV6QxtoLI.jpg",
            "photo_100": "https://pp.userapi.com/c622118/v622118651/e044/P9mVUhXBV58.jpg",
            "photo_200": "https://pp.userapi.com/c622118/v622118651/e043/Soq8oxCMB0I.jpg"
        },
        {
            "id": 76709587,
            "name": "Prosvet",
            "screen_name": "prosvet_pub",
            "is_closed": 0,
            "type": "page",
            "is_admin": 0,
            "is_member": 0,
            "photo_50": "https://pp.userapi.com/c630431/v630431500/b24a/GHox8AmDTXU.jpg",
            "photo_100": "https://pp.userapi.com/c630431/v630431500/b249/H3mcC-K7htM.jpg",
            "photo_200": "https://pp.userapi.com/c630431/v630431500/b248/9fyvB8gkcwc.jpg"
        }
    ],
    "next_from": "1/4105_1514494800_5"
}

}

我需要从这个JSON获得的是：＆＃34; text＆＃34;，＆＃34; comments＆＃34;，＆＃34; likes＆＃34;，＆＃34; reposts＆＃34;， ＆＃34;附件＆＃34;

内部＆＃34;附件＆＃34;我希望得到的领域＆＃34; photo_604＆＃34;线。

这是我的代码：

class NewsItems: Decodable {
    var text: String?
    var comments: Comments
    var likes: Likes
    var reposts: Reposts
    var attachments: [Attachments]
}

class Comments: Decodable {
    var count: Int?
}

class Likes: Decodable {
    var count: Int?
}

class Reposts: Decodable {
    var count: Int?
}

class Attachments: Decodable {
    var attachments: AttachmentPhoto
}

class AttachmentPhoto: Decodable {
    var photo: WhatIsInsideAttachmentsPhoto
}

class WhatIsInsideAttachmentsPhoto: Decodable {
    var photo: String?

    enum CodingKeys: String, CodingKey {
        case photo = "photo_604"
    }
}


class WhatIsIsideResponseNewsFeed: Decodable {
    var items: [NewsItems]
}

public class ResponseNewsFeed: Decodable {
    var response: WhatIsIsideResponseNewsFeed
}

但在提出请求后：

Alamofire.request(baseURL+methodName, parameters: parameters).responseData(completionHandler: { response in
        if let result = response.result.value {
            let decoder = JSONDecoder()
            let myResponse = try! decoder.decode(ResponseNewsFeed.self, from: result)
            completion(myResponse.response.items)

我收到错误：

  

致命错误：＆＃39;尝试！＆＃39;表达式意外地引发了一个错误：   Swift.DecodingError.keyNotFound（_UL_PetrovLeonid.NewsItems。（CodingKeys   在_FA9A2FC8130449AA328C19ACD9506C2D）。附件中，   Swift.DecodingError.Context（codingPath：   [_UL_Leonid.ResponseNewsFeed。（CodingKeys in   。_FA9A2FC8130449AA328C19ACD9506C2D）.response，_UL_PetrovLeonid.WhatIsIsideResponseNewsFeed（在_FA9A2FC8130449AA328C19ACD9506C2D）.items CodingKeys，基金会（_ JSONKey在_12768CA107A31EF2DCE034FD75B541C9）（stringValue的：＆＃34;指数0＆＃34 ;,的intValue：可选（0））]，debugDescription：＆＃ 34;没有与密钥相关的值   附件（\＆＃34;附件\＆＃34;）。＆＃34;，underlyingError：nil））

为什么会发生这种情况，我需要做些什么来解决它？我从现在起只用了三个月就开始编码了，所以如果我的问题看起来很傻，请事先原谅我。

谢谢。

1 个答案:

答案 0 :(得分：1)

错误信息非常清楚

  

... Swift.DecodingError。 keyNotFound ... NewsItems。（_FA9A2FC8130449AA328C19ACD9506C2D中的CodingKeys ）。附件 ... 没有与关键附件相关联的值（\＆＃34;附件\＆＃34;）。

  • keyNotFound 缺少关键
  • NewsItems。（CodingKeys ...）。附件是attachments中NewsItems的关键Attachments的对象，attachments
  • 没有与关键附件相关联的值（\＆＃34;附件\＆＃34;）就是这样说的。

很快：Attachments中没有关键 "attachments": [ { "type": "photo", "photo": { ，这是真的。

看看你的JSON 

class Attachments: Decodable {
    let type : String
    let photo : AttachmentPhoto
}

等效类是

AttachmentPhoto

class AttachmentPhoto: Decodable { private enum CodingKeys : String, CodingKey { case photo604 = "photo_604" case id } let id : Int let photo604 : String // or even URL // etc. } 应该是

class

实际上没有必要使用struct es，在大多数情况下gcloud ml-engine jobs submit training test${JOB_ID} \ --stream-logs \ --module-name trainer.task \ --package-path trainer\ --staging-bucket ${BUCKET_NAME} \ --region us-central1 \ --runtime-version=1.2 \ -- \ --output_path "${GCS_PATH}/training" \ --eval_data_paths "${GCS_PATH}/preproc/eval*" \ --train_data_paths "${GCS_PATH}/preproc/train*" 就足够了。

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