Swift's Encodable/Decodable protocols, released with Swift 4, make JSON (de)serialization quite pleasant. However, I have not yet found a way to have fine-grained control over which properties should be encoded and which should get decoded.
I have noticed that excluding the property from the accompanying CodingKeys enum excludes the property from the process altogether, but is there a way to have more fine-grained control?
ベストアンサー1
エンコード/デコードするキーのリストは、 と呼ばれる型によって制御されますCodingKeys(s末尾の に注意してください)。コンパイラはこれを合成できますが、いつでもオーバーライドできます。
nickname両方のエンコードからプロパティを除外したいとしますそしてデコード:
struct Person: Codable {
var firstName: String
var lastName: String
var nickname: String?
private enum CodingKeys: String, CodingKey {
case firstName, lastName
}
}
非対称にしたい場合（つまり、エンコードするがデコードしない、またはその逆）、encode(with encoder: )との独自の実装を提供する必要がありますinit(from decoder: )。
struct Person: Codable {
var firstName: String
var lastName: String
// Since fullName is a computed property, it's excluded by default
var fullName: String {
return firstName + " " + lastName
}
private enum CodingKeys: String, CodingKey {
case firstName, lastName, fullName
}
// We don't want to decode `fullName` from the JSON
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
firstName = try container.decode(String.self, forKey: .firstName)
lastName = try container.decode(String.self, forKey: .lastName)
}
// But we want to store `fullName` in the JSON anyhow
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(firstName, forKey: .firstName)
try container.encode(lastName, forKey: .lastName)
try container.encode(fullName, forKey: .fullName)
}
}