忽略 swift Codable 中的以下属性？

Question

我有这个帐户结构。当我发送“POST”端点并使用它们return成功解码到swift对象[=12时，我想忽略以下属性环境和编码到JSON对象的Id =]

更新我有这个错误属性类型 '[Environment]' 与它的包装类型 'wrappedValue' 属性不匹配 'SkipEncode'

struct Account: Codable {
    let accountID, displayName, managedByID, id: String
    let environments: [Environment]
    let contacts: [Contact]

    enum CodingKeys: String, CodingKey {
        case accountID
        case displayName
        case managedID
        case id
        case environments
        case contacts
    }
}

Answer 1

如果要忽略，比如environments编码的时候，可以定义自己的编码实现：

struct Account: Codable {
    let accountID, displayName, managedByID, id: String
    let environments: [Environment]
    let contacts: [Contact]

    enum CodingKeys: String, CodingKey {
        case accountID, displayName, managedByID, id, environments, contacts
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(accountID, forKey: .accountID)
        try container.encode(displayName, forKey: .displayName)
        // ... just don't include the environments here
    }
}

Answer 2

另一种方法，如果您不想手动实现 encode(to:) 并放弃 Codable 自动合成的好处，您可以创建一个属性包装器作为一种方式标记要跳过的属性：

@propertyWrapper
struct SkipEncode<T> {
   var wrappedValue: T
}

extension SkipEncode: Decodable where T: Decodable {
   init(from decoder: Decoder) throws {
      let container = try decoder.singleValueContainer()
      self.wrappedValue = try container.decode(T.self)
   }
}

extension SkipEncode: Encodable {
   func encode(to encoder: Encoder) throws {
      // nothing to do here
   }
}

extension KeyedEncodingContainer {
   mutating func encode<T>(_ value: SkipEncode<T>, forKey key: K) throws {
      // overload, but do nothing
   }
}

那么你可以像这样使用 @SkipEncode:

struct Account: Codable {
    let accountID, displayName, managedByID: String
    let contacts: [Contact]
    
    @SkipEncode
    let id: String

    @SkipEncode 
    let environments: [Environment]
}

Answer 3

按照 NewDev 建议的方法跟进。如果你想实现一个属性包装器，你需要实现一个通用的包装器才能跳过任何属性，而不仅仅是字符串：

@propertyWrapper
struct SkipEncode<T: Decodable> {
   var wrappedValue: T
}

extension SkipEncode: Codable {
    init(from decoder: Decoder) throws {
       wrappedValue = try decoder.singleValueContainer().decode(T.self)
    }
    func encode(to encoder: Encoder) throws { }
}

extension KeyedEncodingContainer {
    mutating func encode<T>(_ value: SkipEncode<T>, forKey key: K) throws { }
}

游乐场测试：

结构环境：可编码{} 结构联系人：Codable { }

struct Account: Codable {
    let accountID, displayName, managedByID: String

    @SkipEncode
    var id: String

    @SkipEncode
    var environments: [Environment]
    
    let contacts: [Contact]
}

let account = Account.init(accountID: "account", displayName: "name", managedByID: "manager", id: "id", environments: [], contacts: [])
let dt = try JSONEncoder().encode(account)
print(String.init(data: dt, encoding: .utf8)!) // {"accountID":"account","contacts":[],"managedByID":"manager","displayName":"name"}

忽略 swift Codable 中的以下属性？

ignore the following properties in swift Codable?

json

swift

urlsession

codable