Swift Core数据存储自定义类返回零

Question

我想用自定义对象存储到核心数据的数组。我想用自定义类存储两个阵列。第一个将是检查点，如阵列＆lt; [checkpoint]＆gt;第二个将作为数组轨迹。这是数据模型：数据模型

import Foundation
import CoreData

public class Checkpoint: NSObject, NSCoding {
    public static var supportsSecureCoding = true

    public var longitude:Double?
    public var latitude:Double?
    public var instruction:String?
    public var tts:Bool?
    public var len_track:Int?

    init(longitude: Double, latitude: Double, instruction: String, tts: Bool, len_track: Int) {
        self.longitude = longitude
        self.latitude = latitude
        self.instruction = instruction
        self.tts = tts
        self.len_track = len_track
    }

    public func encode(with coder: NSCoder) {
        coder.encode(longitude, forKey: "longitude")
        coder.encode(latitude, forKey: "latitude")
        coder.encode(instruction, forKey: "instruction")
        coder.encode(tts, forKey: "tts")
        coder.encode(len_track, forKey: "len_track")
    }

    public required init?(coder: NSCoder) {
        guard let longitude = coder.decodeObject(forKey: "longitude") as? Double,
              let latitude = coder.decodeObject(forKey: "latitude") as? Double,
              let instruction = coder.decodeObject(forKey: "instruction") as? String,
              let tts = coder.decodeObject(forKey: "tts") as? Bool,
              let len_track = coder.decodeObject(forKey: "len_track") as? Int else {
            return nil
        }
        self.longitude = longitude
        self.latitude = latitude
        self.instruction = instruction
        self.tts = tts
        self.len_track = len_track
    }
}

public class Coordinates: NSObject, NSCoding {
    public static var supportsSecureCoding = true

    var latitude: Float?
    var longitude: Float?

    init(longitude: Float, latitude: Float) {
        self.longitude = longitude
        self.latitude = latitude
    }

    public func encode(with coder: NSCoder) {
        coder.encode(longitude, forKey: "longitude")
        coder.encode(latitude, forKey: "latitude")
    }

    public required init?(coder: NSCoder) {
        guard let longitude = coder.decodeObject(forKey: "longitude") as? Float,
              let latitude = coder.decodeObject(forKey: "latitude") as? Float else {
            return nil
        }
        self.longitude = longitude
        self.latitude = latitude
    }
}

与两个可转换实体相距甚远，一切都可以正常存储。但是，当我添加检查点并跟踪到路由时，我会收到以下错误：

Thread 1: "*** -decodeObjectForKey: cannot be sent to an abstract object of class NSCoder: Create a concrete instance!"