为UIColor实现Codable

Question

是否可以实现Encodable和Decodable属性UIColor

当我尝试添加Decodable扩展时,我收到错误

extension UIColor : Decodable {
    public required init(from decoder: Decoder) throws {
        self.init(red: 1, green: 1, blue: 1, alpha: 1)
    }
}

错误:ColorStuff.playground:98:21:错误:初始化程序要求'init(from :)'只能通过required初始化程序在非最终类'UIColor'的定义中满足公共必需的init(来自解码器:解码器)抛出{

我错过了一些明显的东西吗？

我对Encodable扩展没有任何问题- 这似乎是一个Decodable问题.

错误消息告诉我,由于无法访问UIColor类定义,我无法执行此操作

Answer 1

由于编译器给出的错误,您无法在扩展中进行UIColor符合Decodable.

一种解决方案是制作Codable包装类型并使用它.

既然UIColor已经符合NSCoding,那么我们只需编写一个泛型类型,这样我们就可以编码和解码符合的任何内容NSCoding.

import UIKit

struct WrapperOfNSCoding<Wrapped>: Codable where Wrapped: NSCoding {
    var wrapped: Wrapped

    init(_ wrapped: Wrapped) { self.wrapped = wrapped }

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let data = try container.decode(Data.self)
        guard let object = NSKeyedUnarchiver.unarchiveObject(with: data) else {
            throw DecodingError.dataCorruptedError(in: container, debugDescription: "failed to unarchive an object")
        }
        guard let wrapped = object as? Wrapped else {
            throw DecodingError.typeMismatch(Wrapped.self, DecodingError.Context(codingPath: container.codingPath, debugDescription: "unarchived object type was \(type(of: object))"))
        }
        self.wrapped = wrapped
    }

    func encode(to encoder: Encoder) throws {
        let data = NSKeyedArchiver.archivedData(withRootObject: wrapped)
        var container = try encoder.singleValueContainer()
        try container.encode(data)
    }
}

let colors = [UIColor.red, UIColor.brown]
print(colors)
let jsonData = try! JSONEncoder().encode(colors.map({ WrapperOfNSCoding($0) }))
let colors2 = try! JSONDecoder().decode([WrapperOfNSCoding<UIColor>].self, from: jsonData).map({ $0.wrapped })
print(colors2)