iOS( swift ): Encoding/Decoding Enums

Question

我有一些 NSObject 的子类，它定义了一个可表示的字符串 Enum，如下所示:

class SomeClass: NSObject {

    enum Direction: String {
        case north = "North"
        case south = "South"
    }

    public var direction: Direction

    init(direction: Direction) {
        self.direction = direction
        super.init()
    }

}

我想允许这个类被编码和解码，所以我使用如下:

func encode(with aCoder: NSCoder) {
    aCoder.encode(direction, forKey: #keyPath(direction))
}

public convenience required init?(coder aDecoder: NSCoder) {
    self.init(direction: aDecoder.decodeObject(forKey: #keyPath(direction)) as! Direction)
}

但是，当我更改 direction 的定义时，出现以下错误 Argument of '#keyPath' refers to non-'@objc' property 'direction'到

@objc public var direction: Direction

我收到错误消息Property cannot be marked @objc because its type cannot be represented in Objective-C。

请问避免此错误的最佳方法是什么？

感谢您的帮助。

编辑

评论说明了问题。此链接中的答案建议如何使用 String 原始表示来完成。

How to make a Swift String enum available in Objective-C?

Answer 1

您可以利用基于String 的枚举(不仅)具有的rawValue 支持:

func encode(with aCoder: NSCoder) {
    aCoder.encode(direction.rawValue, forKey: "direction")
}

public convenience required init?(coder aDecoder: NSCoder) {
    guard let direction = Direction(rawValue: aDecoder.decodeObject(forKey: "direction") else {
        // direction was not encoded, we assume an encoding error
        return nil
    }
    self.init(direction: direction)
}