[英]Type 'X' does not conform to protocol 'Encodable'
我希望在这里能够理解这个错误,并且可能对可编码和可解码的更广泛理解。 我班级的一部分如下:
public var eventId: String?
public var eventName: String?
public var eventDescription: String?
public var location: CLLocation?
/// These properties will be encoded/decoded from JSON
private enum CodingKeys: String, CodingKey {
case eventId
case eventName
case eventDescription
case location
}
public required convenience init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let eventId = try container.decode(String?.self, forKey: .eventId)
let eventName = try container.decode(String?.self, forKey: .eventName)
let location = try container.decode(CLLocation?.self, forKey: .location)
self.init(eventId: eventId, eventName: eventName, location:location)
}
这个类非常有效,直到我添加位置。 当我这样做时,我得到两个错误:类型'CAEvent'不符合协议'可编码',并且在fromDecoder方法内没有上下文类型'无法解析'引用成员'位置'。 有人可以解释这个问题吗?
我google并发现了一篇文章 ,它提供了不可编码CLLocation
。
阅读该文章后,很难为CLLocation实现Decodable
。 但是作者使用另一个struct Location
来解码CLLocation
对象。 这很有趣也很棘手。
extension CLLocation: Encodable {
enum CodingKeys: String, CodingKey {
case latitude
case longitude
case altitude
case horizontalAccuracy
case verticalAccuracy
case speed
case course
case timestamp
}
public func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(coordinate.latitude, forKey: .latitude)
try container.encode(coordinate.longitude, forKey: .longitude)
try container.encode(altitude, forKey: .altitude)
try container.encode(horizontalAccuracy, forKey: .horizontalAccuracy)
try container.encode(verticalAccuracy, forKey: .verticalAccuracy)
try container.encode(speed, forKey: .speed)
try container.encode(course, forKey: .course)
try container.encode(timestamp, forKey: .timestamp)
}
}
struct Location: Codable {
let latitude: CLLocationDegrees
let longitude: CLLocationDegrees
let altitude: CLLocationDistance
let horizontalAccuracy: CLLocationAccuracy
let verticalAccuracy: CLLocationAccuracy
let speed: CLLocationSpeed
let course: CLLocationDirection
let timestamp: Date
}
extension CLLocation {
convenience init(model: Location) {
self.init(coordinate: CLLocationCoordinate2DMake(model.latitude, model.longitude), altitude: model.altitude, horizontalAccuracy: model.horizontalAccuracy, verticalAccuracy: model.verticalAccuracy, course: model.course, speed: model.speed, timestamp: model.timestamp)
}
}
///
struct Person {
let name: String
let location: CLLocation
enum CodingKeys: String, CodingKey {
case name
case location
}
}
extension Person: Decodable {
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
let name = try values.decode(String.self, forKey: .name)
// Decode to `Location` struct, and then convert back to `CLLocation`.
// It's very tricky
let locationModel = try values.decode(Location.self, forKey: .location)
location = CLLocation(model: locationModel)
}
}
根据您希望位置包含的内容,您可以添加第二个JSON兼容变量,该变量在解码器中处理以创建CLLocation。 这不是解码完整的CLLocation,但可能就是您所需要的
public var eventId: String?
public var eventName: String?
public var eventDescription: String?
public var location: [Float]? // latitude, longitude
public var cllocation: CLLocation?
/// These properties will be encoded/decoded from JSON
private enum CodingKeys: String, CodingKey {
case eventId
case eventName
case eventDescription
case location
}
public required convenience init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let eventId = try container.decode(String?.self, forKey: .eventId)
let eventName = try container.decode(String?.self, forKey: .eventName)
let location = try container.decode([Float]?.self, forKey: .location)
let cllocation = CLLocation(latitude: CLLocationDegrees(location[0]), CLLocationDegrees(longitude[1]))
self.init(eventId: eventId, eventName: eventName, location:cllocation)
}
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