我有一个拥有可变属性的实体。它是一个自定义对象数组,Reminder
遵循 NSSecureCoding
协议。
@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)
}
}
以下是我的代码。
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")
}
在初始化NSPersistantContainer
之前,我使用以下代码注册了ReminderDataTransformer
。
ValueTransformer.setValueTransformer(ReminderDataTransformer(), forName: .reminderToDataTransformer)
我在 xCode 的数据模型检查器中使用了 ReminderToDataTransformer
作为转换器。
但是,当保存实体时,由于以下错误而导致它无法正常工作。
[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)
更新
没有例外。当第二次启动应用程序时,此错误将被记录在控制台中。
[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]'.
如果我把代码改为存储Reminder
而不是[Reminder]
,那么我就不能正确地对Reminder的数组进行编码/解码。
只是为了明确,我可以存储Reminder
,但不能存储[Reminder]
。
如何将[Reminder]
存储为Transformable
?