在Swift中实现NSCoding协议有什么问题

Question

我认为我会谨慎,并通过转换一个类来尝试在现有的Obj-C项目上使用Swift.还有一个小而简单的.噢亲爱的.

将原始的obj-c音译为Swift应该是直截了当的,所以看起来如此.不幸的是,虽然编码器到持久存储似乎有效,但它在init编码器的第一行出现EXC_BREAKPOINT错误而崩溃.

IF(和大写是有意的)NSCoding/Swift提供与NSCoding/ObjC相同的持久内容,然后我的所有obj-c版本应该能够读取Swift编码的内容,反之亦然.事实证明并非如此 - 当我试图从Swift版本中读取持久性存储时,我完美运行的obj-c版本崩溃了.当然,如果NSCoding正确实现,它应该生成一个可读的东西吗？否则,应该有单独的NSCodingSwift和NSCodingObjC协议？

总而言之,我可以在obj-c中读/写.我不能写/ obj-c和read/swift我可以写/ swift read/obj-c而且我无法在swift中读/写.

以下是两个版本:

let keyBeaconItemNameKey = "name"
let keyBeaconItemUUIDKey = "uuid"
let keyBeaconItemMajorValueKey = "major"
let keyBeaconItemMinorValueKey = "minor"

import UIKit
import CoreLocation

class SMBeaconItem : NSObject, NSCoding
{
    var name : String!
    var uuid : NSUUID!
    var major : NSNumber!
    var minor : NSNumber!

    init(newName : String, newUUID : NSUUID, newMajor : NSNumber, newMinor : NSNumber )
    {
        name = newName
        uuid = newUUID
        major = newMajor
        minor = newMinor
    }

    init( coder decoder : NSCoder!)
    {
        name = decoder.decodeObjectForKey(keyBeaconItemNameKey) as String
        uuid = decoder.decodeObjectForKey(keyBeaconItemUUIDKey) as NSUUID
        major = decoder.decodeObjectForKey(keyBeaconItemMajorValueKey) as NSNumber
        minor = decoder.decodeObjectForKey(keyBeaconItemMinorValueKey) as NSNumber
    }

    func encodeWithCoder( encoder: NSCoder!)
    {
        encoder.encodeObject(name, forKey:keyBeaconItemNameKey)
        encoder.encodeObject(uuid, forKey:keyBeaconItemUUIDKey)
        encoder.encodeObject(major, forKey:keyBeaconItemMajorValueKey)
        encoder.encodeObject(minor, forKey:keyBeaconItemMinorValueKey)
       }
    }

工作原创:

@implementation SMBeaconItem

- (instancetype)initWithName:(NSString *)name uuid:(NSUUID *)uuid major:(CLBeaconMajorValue)major minor:(CLBeaconMinorValue)minor
{
    self = [super init];
    if (!self)
    {
        return nil;
    }

    _name = name;
    _uuid = uuid;
    _majorValue = major;
    _minorValue = minor;

    return self;
}

#pragma mark - Persistence

- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (!self)
    {
        return nil;
    }

    _name = [aDecoder decodeObjectForKey:keyBeaconItemNameKey];
    _uuid = [aDecoder decodeObjectForKey:keyBeaconItemUUIDKey];
    _majorValue = [[aDecoder decodeObjectForKey:keyBeaconItemMajorValueKey] unsignedIntegerValue];
    _minorValue = [[aDecoder decodeObjectForKey:keyBeaconItemMinorValueKey] unsignedIntegerValue];

    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.name forKey:keyBeaconItemNameKey];
    [aCoder encodeObject:self.uuid forKey:keyBeaconItemUUIDKey];
    [aCoder encodeObject:[NSNumber numberWithUnsignedInteger:self.majorValue] forKey:keyBeaconItemMajorValueKey];
    [aCoder encodeObject:[NSNumber numberWithUnsignedInteger:self.minorValue] forKey:keyBeaconItemMinorValueKey];
}

@end

谢谢你提供的所有帮助.

Answer 1

对我来说唯一突出的是您使用的是String而不是NSStringas thename类型。在苹果发布的测试版中，String（奇怪的是）并不是NSString. 即缺少一些方法，需要调用.bridgeToObjectiveC()才能获取NSString版本。使用该类型可能会符合预期NSCoder，但差异不应该如此。

我实际上没有测试这个说法，因为我不在我的开发机器上。但这是我的直觉。尝试一下，看看会发生什么！如果没有任何变化，请尝试切换设置变量的顺序，看看是否是与字段相关的问题name或仅仅是 init 函数的第一行的问题。