Swift Codable 协议…编码/解码 NSCoding 类

Question

我有以下结构……

struct Photo: Codable {

    let hasShadow: Bool
    let image: UIImage?

    enum CodingKeys: String, CodingKey {
        case `self`, hasShadow, image
    }

    init(hasShadow: Bool, image: UIImage?) {
        self.hasShadow = hasShadow
        self.image = image
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        hasShadow = try container.decode(Bool.self, forKey: .hasShadow)

        // This fails
        image = try container.decode(UIImage?.self, forKey: .image) 
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(hasShadow, forKey: .hasShadow)

        // This also fails
        try container.encode(image, forKey: .image)
    }
}

编码 Photo 失败，显示...

Optional does not conform to Encodable because UIImage does not conform to Encodable

解码失败...

Key not found when expecting non-optional type Optional for coding key \"image\""))

有没有办法对 Swift 对象进行编码，这些对象包含符合 NSCoding（UIImage、UIColor 等）的 NSObject 子类属性？

Answer 1

感谢@vadian 给我指点 encoding/decoding Data…

class Photo: Codable {

    let hasShadow: Bool
    let image: UIImage?

    enum CodingKeys: String, CodingKey {
        case hasShadow, imageData
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        hasShadow = try container.decode(Bool.self, forKey: .hasShadow)

        if let imageData = try container.decodeIfPresent(Data.self, forKey: .imageData) {
            image = NSKeyedUnarchiver.unarchiveObject(with: imageData) as? UIImage
        } else {
            image = nil
        }
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(hasShadow, forKey: .hasShadow)

        if let image = image {
            let imageData = NSKeyedArchiver.archivedData(withRootObject: image)
            try container.encode(imageData, forKey: .imageData)
        }
    }
}

Swift Codable 协议…编码/解码 NSCoding 类

Swift Codable protocol… encoding / decoding NSCoding classes

nscoding

swift

swift4

codable