กลยุทธ์การถอดรหัสคีย์และวันที่

ภาพรวมกลยุทธ์การถอดรหัส

import Foundation

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
print("Strategy configured")

convertFromSnakeCase

import Foundation

struct User: Codable {
    var firstName: String
    var lastName: String
}

let json = "{\"first_name\":\"Ada\",\"last_name\":\"Lovelace\"}"
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let u = try decoder.decode(User.self, from: json.data(using: .utf8)!)
print(u.firstName, u.lastName)

การเข้ารหัสเป็นรูปแบบขีดล่าง

import Foundation

struct User: Codable {
    var firstName: String
}

let encoder = JSONEncoder()
encoder.keyEncodingStrategy = .convertToSnakeCase
let data = try encoder.encode(User(firstName: "Ada"))
print(String(data: data, encoding: .utf8)!)

กลยุทธ์ใช้กับคีย์ทั้งหมด

import Foundation

struct Meta: Codable { var createdAt: String }
struct Doc: Codable { var docTitle: String; var docMeta: Meta }

let json = "{\"doc_title\":\"A\",\"doc_meta\":{\"created_at\":\"now\"}}"
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let d = try decoder.decode(Doc.self, from: json.data(using: .utf8)!)
print(d.docTitle, d.docMeta.createdAt)

ปัญหาเรื่องวันที่

import Foundation

struct Event: Codable {
    var name: String
    var date: Date
}

print("Date needs a strategy to parse")

การถอดรหัสวันที่แบบ ISO-8601

import Foundation

struct Event: Codable {
    var name: String
    var date: Date
}

let json = "{\"name\":\"Launch\",\"date\":\"2020-01-01T00:00:00Z\"}"
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let e = try decoder.decode(Event.self, from: json.data(using: .utf8)!)
print(e.date.timeIntervalSince1970)

การเข้ารหัสวันที่แบบ ISO-8601

import Foundation

struct Event: Codable {
    var name: String
    var date: Date
}

let e = Event(name: "Launch", date: Date(timeIntervalSince1970: 1577836800))
let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .iso8601
let data = try encoder.encode(e)
print(String(data: data, encoding: .utf8)!)

กลยุทธ์ secondsSince1970

import Foundation

struct Event: Codable {
    var date: Date
}

let json = "{\"date\":1577836800}"
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .secondsSince1970
let e = try decoder.decode(Event.self, from: json.data(using: .utf8)!)
print(e.date.timeIntervalSince1970)

รูปแบบวันที่ที่กำหนดเอง

import Foundation

struct Event: Codable { var date: Date }

let fmt = DateFormatter()
fmt.dateFormat = "yyyy-MM-dd"
fmt.timeZone = TimeZone(identifier: "UTC")
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .formatted(fmt)
let e = try decoder.decode(Event.self, from: "{\"date\":\"2020-01-01\"}".data(using: .utf8)!)
print(e.date.timeIntervalSince1970)

การรวมกลยุทธ์

import Foundation

struct LogEntry: Codable {
    var eventName: String
    var occurredAt: Date
}

let json = "{\"event_name\":\"login\",\"occurred_at\":\"2020-01-01T00:00:00Z\"}"
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
decoder.dateDecodingStrategy = .iso8601
let entry = try decoder.decode(LogEntry.self, from: json.data(using: .utf8)!)
print(entry.eventName, entry.occurredAt.timeIntervalSince1970)

กลยุทธ์เทียบกับ CodingKeys

import Foundation

struct Item: Codable {
    var itemName: String
}

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let i = try decoder.decode(Item.self, from: "{\"item_name\":\"Pen\"}".data(using: .utf8)!)
print(i.itemName)

ตรวจความเข้าใจอย่างรวดเร็ว: กลยุทธ์

ทบทวน: กลยุทธ์คีย์และวันที่