json - JSON 序列化后子类属性崩溃

Question

我有一个最奇怪的问题。在执行 JSON 序列化并创建对象后，代码在尝试访问子类的任何属性时崩溃。当我尝试访问对象父类(super class)的属性时，它们会被正确打印。

这是类:

import UIKit

class Patient: Person {
    var approved: Bool
    var doctorId: Int

    private enum CodingKeys: String, CodingKey {
        case approved
        case doctorId
    }

    init(id: String, name: String, lastName: String, phoneNumber: String, email: String, imageURL:URL, approved:Bool, doctorId:Int) {
        self.approved = approved
        self.doctorId = doctorId
        super.init(id: id, firstName: name, lastName: lastName, imageURL: imageURL)
    }

    required init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        self.approved  = try values.decode(Bool.self, forKey: .approved)
        self.doctorId = try values.decode(Int.self, forKey: .doctorId)
        try super.init(from: decoder)
    }

    var description: String {
        return "\(type(of: self)) - (\(self.firstName), \(self.lastName))" //superclass properties 
    }
}

struct PatientsList : Codable {
    let patients: [Patient]
}

人类:

class Person: Codable {
    let firstName: String
    let lastName: String
    let imageURL: URL?
    let id: String

    private enum CodingKeys: String, CodingKey {
        case firstName
        case lastName
        case imageURL = "profileImgPath"
        case id = "_id"
    }

    init(id: String, firstName: String, lastName: String, imageURL:URL) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName
        self.imageURL = imageURL
    }

    required init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        self.id = try values.decode(String.self, forKey: .id)
        self.firstName = try values.decode(String.self, forKey: .firstName)
        self.lastName = try values.decode(String.self, forKey: .lastName)
        self.imageURL = try values.decodeIfPresent(URL.self, forKey: .imageURL)
    }
}

这是我执行序列化的方式:

do {
                    let jsonData = try JSONSerialization.data(withJSONObject: JSON, options: [])
                    let decoder = JSONDecoder()
                    let patientList = try! decoder.decode(PatientsList.self, from: jsonData)
                    completionBlock(.success(patientList.patients))
                } catch {
                    print(error.localizedDescription)
                }

这里是 //在控制台中:po(patient.approved) 打印 false //在控制台中:表达式转储(患者)

▿ iHeal.Patient #0 ▿ super: iHeal.Person

firstName: "Sarah"

lastName: "Connor"

imageURL: nil

id: "5b367491052aaca6489e4805"

birthDate: "1980-06-10T00:00:00.000Z"

approved: false

doctorId: 12

print(patient.approved) //crash
print(patient.doctorId) // if I comment out previous line, this one crashes

Thread 1: EXC_BAD_ACCESS (code=1, address=0x200000002)

我可以提到的另一件奇怪的事情:没有在 Patient 上调用 description

print(patient) // prints plain: <Patient: 0x608000141c30>

杰森:

{
    "patients": [
        {
            "approved": false,
            "_id": "5b367491052aaca6489e4805",
            "birthDate": "1980-06-10T00:00:00.000Z",
            "doctorId": 12,
            "firstName": "Sarah",
            "lastName": "Connor"
        },
        {
            "approved": false,
            "drains": [],
            "_id": "5b3674e5052aaca6489e66b3",
            "__v": 0,
            "birthDate": "1980-06-10T00:00:00.000Z",
            "doctorId": 12,
            "firstName": "Sarah",
            "lastName": "Connor"
        }
    ]
}

Answer 1

副本:Crash when accessing Object properties after decoding from JSON

从基类(即 Person)中删除了 Codable 一致性，但您仍然可以通过保持带有 docoder 的 init 方法从子类调用来解码基类成员。子类现在将符合 Codable。