使用可编码将字符串转换为日期/整数/双精度

Question

我从 API 收到响应，但问题是 API 将值作为日期和双精度值字符串发送回。因此，我收到错误"预期解码双倍，但找到了一个字符串/数据。我已经像这样构建了我的结构来解决问题，但这似乎是一个补丁。有没有更好的方法来解决这个问题？我觉得苹果已经想到了这一点，并包含了原生的东西来解决这个问题。

struct SimpleOrder:Codable{ 
var createdDate:Date! {
return createdDateString.dateFromISO8601
}
var createdDateString:String
var orderId:String!
var priceVal:Double!
var priceString:String{
didSet {
priceVal = Double(self.priceString)!
}
}
private enum CodingKeys: String, CodingKey {
//case createdDate
case createdDateString = "time"
case orderId = "id"
case priceVal
case priceString = "price"
}
}

我不知道这是否相关，但这就是它的使用方式。我正在将数据作为字符串获取并将其转换为存储在dataFromString变量中的数据

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601 //This is irrelevant though because the date is returned as a string. 
do{
let beer = try decoder.decode(SimpleOrder.self, from: dataFromString)
print ("beer is (beer)")
}catch let error{
print ("error is (error)")
}

由于使用可编码，我在尝试获取SimpleOrder的空实例时出现错误。在我使用codable之前，我在没有任何参数的情况下使用SimpleOrder()没有任何问题。

错误：无法为没有参数的类型"SimpleOrder"调用初始值设定项

var singlePoint = SimpleOrder()

Answer 1

struct SimpleOrder: Codable {
var created: Date?
var orderId: String?
var price: String?
private enum CodingKeys: String, CodingKey {
case created = "time", orderId = "id", price
}
init(created: Date? = nil, orderId: String? = nil, price: String? = nil) {
self.created = created
self.orderId = orderId
self.price = price
}
}
extension SimpleOrder {
var priceValue: Double? {
guard let price = price else { return nil }
return Double(price)
}
}

---

extension Formatter {
static let iso8601: DateFormatter = {
let formatter = DateFormatter()
formatter.calendar = Calendar(identifier: .iso8601)
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
return formatter
}()
}

---

解码 API 返回的 json 数据：

let jsonData = Data("""
{
"time": "2017-12-01T20:41:48.700Z",
"id": "0001",
"price": "9.99"
}
""".utf8)

---

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .formatted(Formatter.iso8601)
do {
let simpleOrder = try decoder.decode(SimpleOrder.self, from: jsonData)
print(simpleOrder)
} catch {
print(error)
}

---

或者初始化一个没有值的新对象：

var order = SimpleOrder()