ios - 如何使用 Codable 解码具有更改键的 json 响应？

Question

我有来自修复程序 api 的 json 响应。我想将它解码为如下所示的结构。问题是 json 中“rates”的值是一个键值对数组，它有不同的键。

我有第二个结构，必须从这些键值映射。

我该怎么做Codable？

{
    "success": true,
    "timestamp": 1558883585,
    "base": "EUR",
    "date": "2019-05-26",
    "rates": {
        "AED": 4.116371,
        "AFN": 90.160103,
        "ALL": 122.341655,
        "AMD": 536.359254,
        "ANG": 2.097299,
        "AOA": 368.543773,
        "ARS": 50.418429,
        "AUD": 1.618263,
        "AWG": 2.012124,
        "AZN": 1.910752,
        "BAM": 1.955812,
        "BBD": 2.227793,
        "BDT": 94.245988,
        "BGN": 1.956097,
        "BHD": 0.421705,
        "BIF": 2051.459244,
        "BMD": 1.120649,
        "BND": 1.539664,
        "BOB": 7.729394,
        "BRL": 4.508038,
        "BSD": 1.118587,
        "BTC": 0.00014,
        "BTN": 77.755286,
        "BWP": 12.040813,
        "BYN": 2.323273,
        "BYR": 21964.71167,
        "BZD": 2.254689
    }
}

如果我如下更改“ExchangeRate”结构，它很容易解码。但我有“汇率”应该是“ConvertedRate”结构数组的要求。

struct ExchangeRate : Codable {

    let base : String
    let date : String

    let rates : [String:Double] 
}

这就是我需要的。

struct ExchangeRate : Codable {

    let base : String
    let date : String

    let rates : [ConvertedRate] //keys are varied in json

}

struct ConvertedRate : Codable, Comparable{

   let currencyName : String

   let rate : Double

}

标签： iosjsonswiftcodable

Answer 1

init(from:)由于您没有使用“默认行为”，因此您必须编写自定义。

有关Apple 文档的更多信息。

这是一个可能的解决方案：

struct ExchangeRate : Codable {

    let base : String
    let date : String

    let rates : [ConvertedRate]

    enum CodingKeys: String, CodingKey {
        case base
        case date
        case rates
    }

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        base = try values.decode(String.self, forKey: .base)
        date = try values.decode(String.self, forKey: .date)
        let additionalInfo = try values.decode([String: Double].self, forKey: .rates)
        print(additionalInfo)
        rates = additionalInfo.map({ ConvertedRate(name: $0.key, rate: $0.value) })
    }
}

struct ConvertedRate : Codable {
    let currencyName : String
    let rate : Double

    init(name: String, rate: Double) {
        self.currencyName = name
        self.rate = rate
    }
}

旁注：当前代码可以根据需要解码您的 JSON，但它不会按原样重新编码，因为它正在复制 Swift 结构：

{
    "base": "EUR",
    "date": "2019-05-26",
    "rates": [{
        "currencyName": "BSD",
        "rate": 1.118587
    }, {
        "currencyName": "BWP",
        "rate": 12.040813
    }, {
        "currencyName": "BYN",
        "rate": 2.3232729999999999
    }, {
        "currencyName": "BBD",
        "rate": 2.2277930000000001
    }, {
        "currencyName": "BOB",
        "rate": 7.7293940000000001
    }, {
        "currencyName": "BAM",
        "rate": 1.9558120000000001
    }, {
        "currencyName": "AUD",
        "rate": 1.618263
    }, {
        "currencyName": "AFN",
        "rate": 90.160103000000007
    }, {
        "currencyName": "BYR",
        "rate": 21964.711670000001
    }, {
        "currencyName": "BRL",
        "rate": 4.508038
    }, {
        "currencyName": "BMD",
        "rate": 1.120649
    }, {
        "currencyName": "BGN",
        "rate": 1.956097
    }, {
        "currencyName": "BHD",
        "rate": 0.421705
    }, {
        "currencyName": "ANG",
        "rate": 2.097299
    }, {
        "currencyName": "AOA",
        "rate": 368.54377299999999
    }, {
        "currencyName": "BZD",
        "rate": 2.2546889999999999
    }, {
        "currencyName": "ARS",
        "rate": 50.418429000000003
    }, {
        "currencyName": "BTC",
        "rate": 0.00013999999999999999
    }, {
        "currencyName": "BIF",
        "rate": 2051.4592440000001
    }, {
        "currencyName": "AWG",
        "rate": 2.012124
    }, {
        "currencyName": "AED",
        "rate": 4.116371
    }, {
        "currencyName": "AMD",
        "rate": 536.35925399999996
    }, {
        "currencyName": "BDT",
        "rate": 94.245987999999997
    }, {
        "currencyName": "BND",
        "rate": 1.5396639999999999
    }, {
        "currencyName": "BTN",
        "rate": 77.755285999999998
    }, {
        "currencyName": "AZN",
        "rate": 1.910752
    }, {
        "currencyName": "ALL",
        "rate": 122.341655
    }]
}