忽略swift Codable中的以下属性

Question

我有这个Account结构。我想在向JSON对象编码时忽略以下属性环境和Id；POST"；端点并使用它们将成功解码返回到swift对象

更新我遇到此错误属性类型"[Environment]"与其包装类型"SkipEncode"的"wrappedValue"属性的类型不匹配

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

另一种方法是，如果你不想手动实现encode(to:)并放弃Codable自动合成的好处，你可以创建一个属性包装器来标记你想要跳过的属性：

@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
}
}

然后你可以像这样使用@SkipEncode：

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

@SkipEncode
let id: String
@SkipEncode 
let environments: [Environment]
}

Answer 2

如果您想在编码时忽略，例如environments，您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 3

NewDev建议的方法的后续操作。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，以便能够跳过任何属性，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：可编码的｛｝结构联系人：可编码的｛｝

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"}