具有可转换属性的 CoreData 在保存时失败

Question

我想使用 CoreData 并将自定义类属性保存在其中一个实体中。这样做的方法似乎是使用 Transformable：

然后我尝试添加单个元素并将其保存为：

import UIKit;
import CoreData;

public class EntityData: NSObject, NSSecureCoding
{
    public static var supportsSecureCoding: Bool { true }

    public func encode(with coder: NSCoder) {
        coder.encode(self.name, forKey: "name");
    }

    public required init?(coder: NSCoder) {
        self.name = coder.decodeObject(forKey: "name") as? String;
    }

    var name: String?;

    init(name: String?) {
        self.name = name;
    }
}

class ViewController: UIViewController {
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(_: animated);

        let context  = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext;
        
        let entity = Entity(context: context);
        
        entity.id = URL(string: "google.com");
        entity.data = EntityData(name: "Foo");
        
        do {
            try context.save();
        } catch {
            print("While saveing: \(error)");
        }
    }
}

这失败了：

2021-09-30 13:12:58.865312+0400 tmpCoreData[5815:170015] [error] error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034f6040> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034f6040> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
2021-09-30 13:12:58.865530+0400 tmpCoreData[5815:170015] [error] error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
CoreData: error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
2021-09-30 13:12:58.865983+0400 tmpCoreData[5815:170015] [error] error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034e4300> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034e4300> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
2021-09-30 13:12:58.866158+0400 tmpCoreData[5815:170015] [error] error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
CoreData: error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
2021-09-30 13:12:58.866558+0400 tmpCoreData[5815:170015] [error] error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034ec0c0> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034ec0c0> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
2021-09-30 13:12:58.900366+0400 tmpCoreData[5815:170015] [error] error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
CoreData: error: -executeRequest: encountered exception = <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo = (null)
2021-09-30 13:12:58.912131+0400 tmpCoreData[5815:170015] [error] error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034f83c0> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x6000034f83c0> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null)
While saveing: Error Domain=NSCocoaErrorDomain Code=134060 "A Core Data error occurred."

我不确定我做错了什么。这是我所有的代码，我没有添加任何其他内容。

Answer 1

可转换属性需要符合NS(Secure)Coding（不是Codable！）的类以及归档对象的实现。注意NSSecureUnarchiveFromData 错误。

在 Swift 世界中，考虑将属性声明为 String，使用 Codable 将对象编码为 JSON，并添加计算属性以进行无缝转换。