在 Swift 4.2 中解析 JSON 数据时出现 typeMismatch 错误

Question

类型不匹配错误 - 应解码 Array 但找到字典。 我正在使用嵌入在代码中的本地 json 文件。 Json 文件包含有关包的信息。我需要选择值并将它们相应地显示到 tableview 控制器中。请确定我在可编码模型或代码中做错了什么。 JSON 解析未正确处理。

文件格式：

{
  "packages": [
    {
      "name": "Platinum Maksi 6 GB",
      "desc": "Zengin içerikli Platinum Maksi Paketi ile Turkcell Uygulamalarının keyfini sürün!",
      "subscriptionType": "monthly",
      "didUseBefore": true,
      "benefits": [
        "TV+",
        "Fizy",
        "BiP",
        "lifebox",
        "Platinum",
        "Dergilik"
      ],
      "price": 109.90,
      "tariff": {
        "data": "6144",
        "talk": "2000",
        "sms": "100"
      },
      "availableUntil": "1558131150"
    }
]
}

型号： 基础模型

struct Base : Codable {

    let packages : [Package]?

    enum CodingKeys: String, CodingKey {
            case packages = "packages"
    }

    init(from decoder: Decoder) throws {
            let values = try decoder.container(keyedBy: CodingKeys.self)
            packages = try values.decodeIfPresent([Package].self, forKey: .packages)
    }

2) 封装型号：

struct Package : Codable {

    let availableUntil : String?
    let benefits : String?
    let desc : String?
    let didUseBefore : Bool?
    let name : String?
    let price : Int?
    let subscriptionType : String?
    let tariff : Tariff?

    enum CodingKeys: String, CodingKey {
            case availableUntil = "availableUntil"
            case benefits = "benefits"
            case desc = "desc"
            case didUseBefore = "didUseBefore"
            case name = "name"
            case price = "price"
            case subscriptionType = "subscriptionType"
            case tariff = "tariff"
    }

    init(from decoder: Decoder) throws {
            let values = try decoder.container(keyedBy: CodingKeys.self)
            availableUntil = try values.decodeIfPresent(String.self, forKey: .availableUntil)
            benefits = try values.decodeIfPresent(String.self, forKey: .benefits)
            desc = try values.decodeIfPresent(String.self, forKey: .desc)
            didUseBefore = try values.decodeIfPresent(Bool.self, forKey: .didUseBefore)
            name = try values.decodeIfPresent(String.self, forKey: .name)
            price = try values.decodeIfPresent(Int.self, forKey: .price)
            subscriptionType = try values.decodeIfPresent(String.self, forKey: .subscriptionType)
            tariff = try Tariff(from: decoder)
    }

}

关税模型：

struct Tariff : Codable {

    let data : String?
    let sms : String?
    let talk : String?

    enum CodingKeys: String, CodingKey {
            case data = "data"
            case sms = "sms"
            case talk = "talk"
    }

    init(from decoder: Decoder) throws {
            let values = try decoder.container(keyedBy: CodingKeys.self)
            data = try values.decodeIfPresent(String.self, forKey: .data)
            sms = try values.decodeIfPresent(String.self, forKey: .sms)
            talk = try values.decodeIfPresent(String.self, forKey: .talk)
    }

}

我的代码：

var pack = [Package]()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.

    let url = Bundle.main.url(forResource: "packageList", withExtension: "json")!
    do {
        let data = try Data(contentsOf: url)
        pack = try JSONDecoder().decode([Package].self, from: data)
        print(pack)

    } catch {
        print(error)
    }

Answer 1

您正在解码错误的对象。您必须始终解码 JSON 的根对象 Base。

使用base.packages 获取Package 数组

let base = try JSONDecoder().decode(Base.self, from: data)
pack = base.packages

现在您将收到另外两个类型不匹配错误，将benefits 的类型更改为[String]，将price 的类型更改为Double。

您可以显着减少结构：删除所有 CodingKeys 和所有初始化程序并将所有结构成员声明为非可选（删除问号）。

编辑：

要将availableUntil 解码为Date，请将其声明为Date

let availableUntil: Date

并添加自定义日期解码策略，因为该值是一个字符串（如果值为Int会更容易）

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .custom{ decoder -> Date in
    let container = try decoder.singleValueContainer()
    let dateStr = try container.decode(String.self)
    guard let interval = TimeInterval(dateStr) else { throw DecodingError.dataCorruptedError(in: container, debugDescription: "Date string cannot be converted to TimeInterval") }
    return Date(timeIntervalSince1970: interval)
}
let data = try Data(contentsOf: url)
let base = try decoder.decode(Base.self, from: data)
pack = base.packages