将包含字符串键的 JSON 文件解码为 [(Date,Double)]，每个字符串键包含一个键值对

Question

我正在尝试确定如何读取 JSON 文件，该文件由一系列字符串组成，每个字符串下面是一个键值对到 [(Date,Double)] 中。我已经能够通过手动将主键“Time Series (Daily)”添加到 JSON 文件的顶部和 return [(Date,Double)] 下面的结构来做到这一点。我希望能够消除将“时间序列（每日）”添加到 JSON 文件但仍然 return [(Date,Double)] 的步骤。任何关于如何实现这些结果的见解都将不胜感激。

{
    "Time Series (Daily)": { // this entire line is manually added to JSON file
        "20200803": {
            "NAV": 173.94769
        },
        "20200804": {
            "NAV": 174.57441
        },

struct PrincipalTimeSeriesData {

    var timeSeriesDaily: [(Date, Double)]
}

extension PrincipalTimeSeriesData: Decodable {
    
    enum CodingKeys: String, CodingKey {
        case timeSeriesDaily = "Time Series (Daily)"
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        timeSeriesDaily = try container
                .decode([String:PrincipalTimeSeriesDaily].self, forKey: .timeSeriesDaily)
                .map { (dateFormatterPrin.date(from: [=11=])!, .close) }
    }
}

struct PrincipalTimeSeriesDaily {

    let close: Double
    
}

extension PrincipalTimeSeriesDaily: Decodable {

    enum CodingKeys: String, CodingKey {
        case close = "NAV"
    }
}

Answer 1

您可以将数据解码为 [String:PrincipalTimeSeriesDaily]，然后将生成的字典的 keys/values 映射到您想要的格式：

let jsonData = """
{
        "20200803": {
            "NAV": 173.94769
        },
        "20200804": {
            "NAV": 174.57441
        },
}
""".data(using: .utf8)!

let dateFormatterPrin = DateFormatter()
dateFormatterPrin.dateFormat = "yyyyMMdd"


struct PrincipalTimeSeriesDaily {

    let close: Double
    
}

extension PrincipalTimeSeriesDaily: Decodable {

    enum CodingKeys: String, CodingKey {
        case close = "NAV"
    }
}

do {
    let decoded = try JSONDecoder().decode([String:PrincipalTimeSeriesDaily].self, from: jsonData)
    let converedToDateKeysArray = decoded.map { item -> (Date,Double) in
        (dateFormatterPrin.date(from: item.key)!,item.value.close)
    }.sorted { [=10=].0 < .0 }
    print(converedToDateKeysArray)
} catch {
    print(error)
}

将包含字符串键的 JSON 文件解码为 [(Date,Double)]，每个字符串键包含一个键值对

Decode a JSON file that contains string keys each of which contains one key value pair into [(Date,Double)]

arrays

json

swift

jsondecoder