json - Swift - 来自字符串错误的日期

Question

我正在通过 RESTFUL API 获取 JSON 对象并插入到核心数据实体中。

一个这样的实体是约会，这是我的实体属性

extension Appointment {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Appointment> {
        return NSFetchRequest<Appointment>(entityName: "Appointment");
    }

    @NSManaged public var date: Date?
    @NSManaged public var id: Int32
    @NSManaged public var message: String?
    @NSManaged public var patient_name: String?
    @NSManaged public var doctor: Doctor?

}

这是我用来插入实体的代码

for(_,jsonData):(String, JSON) in self.data["appointment"]["list"] {
    // Construct appointment date
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm"
    let appointmentDate = dateFormatter.date(from: jsonData["date"].string!)!
    print(appointmentDate)

    // Preare appointment entity for inserting
    let appointment = NSEntityDescription.insertNewObject(forEntityName: "Appointment", into: moc)
    appointment.setValue(jsonData["id"].int32, forKey: "id")
    appointment.setValue(appointmentDate, forKey: "date")
    appointment.setValue(jsonData["message"].int32, forKey: "message")
    appointment.setValue(jsonData["patient_name"].int32, forKey: "patient_name")
    do {
        try moc.save()
    } catch {
        fatalError("\(error)")
    }
}

这是我从 API 获取的相关 JSON

"appointment": {
    "list": {
        "id": 1,
        "date": "2017-07-03 17:30",
        "message": "Some message is usefule here",
        "patient_name": "John Doe",
        "doctor_id": 4
    }
}

但是当我运行代码时，出现以下错误:

fatal error: unexpectedly found nil while unwrapping an Optional value

代码有什么问题？

谢谢。

Answer 1

在给定的代码中有两种可能的崩溃

let appointmentDate = dateFormatter.date(from: jsonData["date"].string!)!

在上一行中，如果日期值为 null 或使用不同的格式，它将崩溃

appointment.setValue(jsonData["message"].int32, forKey: "message")

这里它可能会崩溃，因为消息来自字符串，但您正在转换为 int32 并且在 Appointment 实体中它被视为字符串并且对于 patient_name 也是如此

请检查下面的更新代码

for(_,jsonData):(String, [String: Any]) in self.data["appointment"]["list"] {
            // Construct appointment date
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd HH:mm"
            var appointmentDate
            if let date = jsonData["date"].string {
                appointmentDate = dateFormatter.date(from: date) // possible crash may be date may be empty or or not given same date format which we used
            }
            print(appointmentDate)

            // Preare appointment entity for inserting
            let appointment = NSEntityDescription.insertNewObject(forEntityName: "Appointment", into: moc)
            appointment.setValue(jsonData["id"].int32, forKey: "id")
            appointment.setValue(appointmentDate, forKey: "date")
            appointment.setValue(jsonData["message"], forKey: "message")// possible crash :: Here you are getting String converting to Int
            appointment.setValue(jsonData["patient_name"].int32, forKey: "patient_name")
            do {
                try moc.save()
            } catch {
                fatalError("\(error)")
            }
        }