如何在 Codable 结构中添加自定义瞬态属性

Question

我遵循了按预期工作的 Codable 结构

struct VideoAlbum: Codable {


 let id, image: String?
 let video, mediaType: JSONNull?
 let type, deleted, createdOn: String?
 let modifiedOn: JSONNull?

  enum CodingKeys: String, CodingKey {
    case id, image, video
    case mediaType = "media_type"
    case type, deleted
    case createdOn = "created_on"
    case modifiedOn = "modified_on"
 }

}

// MARK: 编码/解码助手

class JSONNull: Codable {
public init() {}

public required init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    if !container.decodeNil() {
        throw DecodingError.typeMismatch(JSONNull.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for JSONNull"))
    }
}

public func encode(to encoder: Encoder) throws {
    var container = encoder.singleValueContainer()
    try container.encodeNil()
}
}

现在我需要添加不是来自 API 的自定义属性来跟踪视频位置，所以我修改了它

struct VideoAlbum: Codable {
    
    let id, image: String?
    let video, mediaType: JSONNull?
    let type, deleted, createdOn: String?
    let modifiedOn: JSONNull?
    
    var isPlaying:Bool? // CUSOTM PROPERTY 
    var currentTime:CMTime? // CUSOTM PROPERTY 
    var timeObserver:Any? // CUSOTM PROPERTY  
    var pausedByUser:Bool? // CUSOTM PROPERTY 
    
    enum CodingKeys: String, CodingKey {
        case id, image, video
        case mediaType = "media_type"
        case type, deleted
        case createdOn = "created_on"
        case modifiedOn = "modified_on"

        case isPlaying,pausedByUser
        case currentTime
        case timeObserver
    }
}

然而它显示

错误类型“VideoAlbum”不符合“Decodable”协议

有没有办法不使用某些属性作为 Codable ？

我知道问题是与CMTime和任何我不知道如何解决它

我搜索了很多问题，但所有属性都来自 API，未找到自定义属性 有没有人建议我任何解决方案或替代方法？

Answer 1

如果您不想解码这 4 个属性，只需不要将它们包含在CodingKeys （并且不要忘记为它们显式提供默认值，以便解码器可以正确初始化对象）：

struct VideoAlbum: Codable {

    let id, image: String?
    let video, mediaType: JSONNull?
    let type, deleted, createdOn: String?
    let modifiedOn: JSONNull?

    var isPlaying: Bool? = nil
    var currentTime: CMTime? = nil
    var timeObserver: Any? = nil
    var pausedByUser: Bool? = nil

    enum CodingKeys: String, CodingKey {
        // include only those that you want to decode/encode
        case id, image, video
        case mediaType = "media_type"
        case type, deleted
        case createdOn = "created_on"
        case modifiedOn = "modified_on"
    }
}

Answer 2

首先从类型结构更改为类。 添加不符合 Codable 协议的父类，例如 VideoAlbumStatus 并添加这些自定义属性。 现在只需从父类继承 VideoAlbum。

class VideoAlbumStatus {
    var isPlaying:Bool? // CUSOTM PROPERTY 
    var currentTime:CMTime? // CUSOTM PROPERTY 
    var timeObserver:Any? // CUSOTM PROPERTY  
    var pausedByUser:Bool? // CUSOTM PROPERTY 
}

class VideoAlbum: VideoAlbumStatus, Codable {

    let id, image: String?
    let video, mediaType: JSONNull?
    let type, deleted, createdOn: String?
    let modifiedOn: JSONNull?

    enum CodingKeys: String, CodingKey {
        case id, image, video
        case mediaType = "media_type"
        case type, deleted
        case createdOn = "created_on"
        case modifiedOn = "modified_on"
    }

    //TO DO 
    // init() for VideoAlbum class

}