arrays - 使用 Struct 的 Encodable 协议(protocol)解码 2D 多边形坐标

Question

我正在尝试使用 Swift Struct 的 Encodable 协议(protocol)解析下面的 json。如果我设置 Any 或 AnyObject 的坐标，则会给出错误，指出不符合协议(protocol)。

我知道这可以使用数组和字典来实现，但我不想那样做。

{
    "coordinates": [
        [
            [
                0.148271,
                51.6723432
            ],
            [
                0.148271,
                51.3849401
            ],
            [
                -0.3514683,
                51.3849401
            ],
            [
                -0.3514683,
                51.6723432
            ],
            [
                0.148271,
                51.6723432
            ]
        ]
    ]
} 

struct Geometry: Codable {
    let coordinates: [[[Double]]]

    init(from decoder: Decoder) throws {
        let data = try decoder.container(keyedBy: CodingKeys.self)
        coordinates = try data.decode([[[Double]]].self, forKey: .coordinates)
    }
}

do {
    let decoded = try JSONDecoder().decode(Geometry.self, from: data!)
    print(decoded)
    completionHandler(statusCode, decoded)
} catch {
    print("Failed to encode data.")
    completionHandler(statusCode, nil)
}

如何解决这个问题？

Answer 1

我的建议是使CLLocationCooperative2D符合Codable解码Double的数组

import CoreLocation

extension CLLocationCoordinate2D : Codable {
    public init(from decoder: Decoder) throws {
        var arrayContainer = try decoder.unkeyedContainer()
        if arrayContainer.count == 2 {
            let lat = try arrayContainer.decode(CLLocationDegrees.self)
            let lng = try arrayContainer.decode(CLLocationDegrees.self)
            self.init(latitude: lat, longitude: lng)
        } else {
            throw DecodingError.dataCorruptedError(in: arrayContainer, debugDescription: "Coordinate array must contain two items")
        }
    }

    public func encode(to encoder: Encoder) throws {
        var arrayContainer = encoder.unkeyedContainer()
        try arrayContainer.encode(contentsOf: [latitude, longitude])
    }
}

然后你可以简单地声明Geometry

struct Geometry: Codable {
    let coordinates: [[CLLocationCoordinate2D]]
}