Ios CoreData-存储可转换对象的数组

我有一个实体具有可交易属性。它是一个自定义对象数组，

提醒

，确认为

NSSecureCoding

@objc(Reminder)
public class Reminder: NSObject, NSSecureCoding {
    public static var supportsSecureCoding: Bool = true
    
    
    public var date: Date
    public var isOn: Bool
    
    public  init(date: Date, isOn: Bool) {
        self.date = date
        self.isOn = isOn
    }
    
    struct Keys {
        static var date: String = "date"
        static let isOn: String = "isOn"
    }
    
    public func encode(with aCoder: NSCoder) {
        aCoder.encode(date as NSDate,forKey: Keys.date)
        aCoder.encode(isOn,forKey: Keys.isOn)
    }
    
    required public init?(coder aDecoder: NSCoder) {
        guard let date = aDecoder.decodeObject(of: NSDate.self, forKey: Keys.date) as Date? else {
            return nil
        }
        
        self.date = date
        self.isOn = aDecoder.decodeBool(forKey: Keys.isOn)
    }
}

---

下面的代码是我的

NSSecureUnarchiveFromDataTransformer

class ReminderDataTransformer: NSSecureUnarchiveFromDataTransformer {

    override class func allowsReverseTransformation() -> Bool {
        return true
    }

    override class func transformedValueClass() -> AnyClass {
        return Reminder.self
    }

    override class var allowedTopLevelClasses: [AnyClass] {
        return [Reminder.self]
    }

    override func transformedValue(_ value: Any?) -> Any? {
        guard let data = value as? Data else {
            fatalError("Wrong data type: value must be a Data object; received \(type(of: value))")
        }
        return super.transformedValue(data)
    }

    override func reverseTransformedValue(_ value: Any?) -> Any? {
        guard let reminder = value as? [Reminder] else {
            fatalError("Wrong data type: value must be a Reminder object; received \(type(of: value))")
        }
        return super.reverseTransformedValue(reminder)
    }
}



extension NSValueTransformerName {
    static let reminderToDataTransformer = NSValueTransformerName(rawValue: "ReminderToDataTransformer")
}

ValueTransformer.setValueTransformer(ReminderDataTransformer(), forName: .reminderToDataTransformer)

---

在初始化NSPersistantContainer之前，我已使用以下代码注册了

提醒DataTransformer

class ReminderDataTransformer: NSSecureUnarchiveFromDataTransformer {

    override class func allowsReverseTransformation() -> Bool {
        return true
    }

    override class func transformedValueClass() -> AnyClass {
        return Reminder.self
    }

    override class var allowedTopLevelClasses: [AnyClass] {
        return [Reminder.self]
    }

    override func transformedValue(_ value: Any?) -> Any? {
        guard let data = value as? Data else {
            fatalError("Wrong data type: value must be a Data object; received \(type(of: value))")
        }
        return super.transformedValue(data)
    }

    override func reverseTransformedValue(_ value: Any?) -> Any? {
        guard let reminder = value as? [Reminder] else {
            fatalError("Wrong data type: value must be a Reminder object; received \(type(of: value))")
        }
        return super.reverseTransformedValue(reminder)
    }
}



extension NSValueTransformerName {
    static let reminderToDataTransformer = NSValueTransformerName(rawValue: "ReminderToDataTransformer")
}

ValueTransformer.setValueTransformer(ReminderDataTransformer(), forName: .reminderToDataTransformer)

---

我在xCode的数据模型检查器中使用了

提醒器TodatTransformer

作为变压器

---

但由于在保存实体时发生以下错误，它无法工作

 [error] error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x282ec0780> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x282ec0780> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
2020-12-31 21:44:09.300394+0100 ReminderApp[26406:6247995] [error] error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)

[error]错误：SQLCore dispatchRequest:异常处理请求：，在编码值时引发。用户信息为（空）
CoreData:错误：SQLCore dispatchRequest:异常处理请求：，在编码值时引发。用户信息为（空）
2020-12-31 21:44:09.300394+0100提醒应用[26406:6247995][错误]错误：-executeRequest:编码值时遇到异常=引发。使用userInfo=（null）

更新 也不例外。当第二次启动应用程序时，此错误将记录在控制台中

[error] fault: exception raised during multi-threaded fetch <shared NSSecureUnarchiveFromData transformer> threw while decoding a value. ({
    NSUnderlyingError = "Error Domain=NSCocoaErrorDomain Code=4864 \"value for key 'root' was of unexpected class 'NSArray (0x1fa392238) [/System/Library/Frameworks/CoreFoundation.framework]'. Allowed classes are '{(\n    \"Reminder (0x100fb6920) [/private/var/containers/Bundle/Application/306C3F0B-75AA-4A2D-A934-260B2EB63313/ReminderApp]\”\n)}’.\” UserInfo={NSDebugDescription=value for key 'root' was of unexpected class 'NSArray (0x1fa392238) [/System/Library/Frameworks/CoreFoundation.framework]'. 

[error]错误：解码值时，在多线程获取期间引发异常。({
NSUnderlyingError=“Error Domain=nscocaerordomain Code=4864\”键“root”的值属于意外的类“NSArray（0x1fa39238）[/System/Library/Frameworks/CoreFoundation.framework]”。允许的类为“{（\n\”提醒（0x100fb6920）[/private/var/containers/Bundle/Application/306C3F0B-75AA-4A2D-A934-260B2EB63313/rementerapp]”“.\”UserInfo={NSDebugDescription=键“root”的值属于意外的类“NSArray（0x1fa39238）[/System/Library/Frameworks/CoreFoundation.framework]”。

---

如果我将代码更改为存储

提醒

而不是

[提醒]

，我想我无法正确编码/解码提醒的数组，因为它可以正常工作

为了清楚起见，我可以存储

提醒

，但不能存储

[提醒]

---

如何将

[提醒]

存储为可转换的

如果要取消归档数组，必须将
NSArray
添加到顶级类，这就是我理解错误消息的方式

override class var allowedTopLevelClasses: [AnyClass] {
    return [NSArray.self, Reminder.self]
}


顺便说一下，代替一个可变形的考虑将数组编码为JSON并将其保存为一个简单的字符串。转换可以由计算的属性执行。
该类可以是一个代码少得多的结构
public struct Reminder : Codable {
    public var date: Date
    public var isOn: Bool
}

在
NSManagedObject
子类中创建一个
String
属性

@NSManaged public var cdReminders : String

和计算属性

var reminders : [Reminder] {
    get {
       return (try? JSONDecoder().decode([Reminder].self, from: Data(cdReminders.utf8))) ?? []
    }
    set {
       do {
           let reminderData = try JSONEncoder().encode(newValue)
           cdReminders = String(data: reminderData, encoding:.utf8)!
       } catch { cdReminders = "" }
    }
}

添加到@vadian的答案中，如果您希望包含父数据转换器中允许的顶级类，请尝试

override static var allowedTopLevelClasses: [AnyClass] {
    var allowed = super.allowedTopLevelClasses
    allowed(contentsOf: [Reminder.self])
    
    return allowed
}

当异常发生时，你能设置断点并查看数据吗？@RahulIyer我更新了我的问题。阅读更新部分。非常感谢。谢谢！这帮了大忙。