Swift将可解码结构转换为Dictionary

Question

我创建了一个可解码的结构，用于解析firebase中存储的数据。

struct DiscussionMessage: Decodable {
var message: String
var userCountryCode: String
var userCountryEmoji: String
var messageTimestamp: Double
var userName: String
var userEmailAddress: String
var fcmToken: String?
var question: String?
var recordingUrl: String?
}

我想使用这个结构也将数据存储在firebase中。但我得到了错误：

***由于未捕获的异常"InvalidFirebaseData"而终止应用程序，原因："(setValue:(无法将__SwiftValue类型的对象存储在。只能存储NSNumber、NSString、NSDictionary和NSArray类型的对象。'以NSException 类型的未捕获异常终止

当我像这样存储数据时：

let message = DiscussionMessage(message: messageTextView.text, userCountryCode: userCountryCode, userCountryEmoji: userCountryEmoji, messageTimestamp: timestamp, userName: userName, userEmailAddress: userEmail, fcmToken: nil, question: nil, recordingUrl: nil)       

messagesReference.childByAutoId().setValue(message)

有没有一种方法可以将可解码对象转换为字典，这样我就可以将其存储在firebase中？

Answer 1

您不需要它是可解码的。你需要的是能够对它进行编码(可编码(。因此，首先将您的结构声明为Codable。编码后，您可以使用JSONSerialization jsonObject方法将数据转换为字典：

extension Encodable {
func data(using encoder: JSONEncoder = .init()) throws -> Data { try encoder.encode(self) }
func string(using encoder: JSONEncoder = .init()) throws -> String { try data(using: encoder).string! }
func dictionary(using encoder: JSONEncoder = .init(), options: JSONSerialization.ReadingOptions = []) throws -> [String: Any] {
try JSONSerialization.jsonObject(with: try data(using: encoder), options: options) as? [String: Any] ?? [:]
}
}

---

extension Data {
func decodedObject<D: Decodable>(using decoder: JSONDecoder = .init()) throws -> D {
try decoder.decode(D.self, from: self)
}
}

---

extension Sequence where Element == UInt8 {
var string: String? { String(bytes: self, encoding: .utf8) }
}

---

我也会将srtuct属性声明为常量。如果您需要更改任何值，只需创建一个新对象：

struct DiscussionMessage: Codable {
let message, userCountryCode, userCountryEmoji, userName, userEmailAddress: String
let messageTimestamp: Double
let fcmToken, question, recordingUrl: String?
}

---

let message: DiscussionMessage = .init(message: "message", userCountryCode: "BRA", userCountryEmoji: "🇧🇷", userName: "userName", userEmailAddress: "[e-mail]", messageTimestamp: 1610557474.227274, fcmToken: "fcmToken", question: "question", recordingUrl: nil)
do {
let string = try message.string()
print(string)      // {"fcmToken":"fcmToken","userName":"userName","message":"message","userCountryEmoji":"🇧🇷","userEmailAddress":"[e-mail]","question":"question","messageTimestamp":1610557474.2272739,"userCountryCode":"BRA"}

let dictionary = try message.dictionary()
print(dictionary)  // ["userName": userName, "userEmailAddress": [e-mail], "userCountryEmoji": 🇧🇷, "messageTimestamp": 1610557474.227274, "question": question, "message": message, "fcmToken": fcmToken, "userCountryCode": BRA]

let data = try message.data()      // 218 bytes
let decodedMessages: DiscussionMessage = try data.decodedObject()
print("decodedMessages", decodedMessages)    // ecodedMessages DiscussionMessage(message: "message", userCountryCode: "BRA", userCountryEmoji: "🇧🇷", userName: "userName", userEmailAddress: "[e-mail]", messageTimestamp: 1610557474.227274, fcmToken: Optional("fcmToken"), question: Optional("question"), recordingUrl: nil)
} catch {
print(error)
}

Answer 2

我要抛出一个答案，看看它是否有帮助。

我建议扩展Encodable，允许任何符合条件的对象返回自己的字典，该字典可以写入Firebase。

这是的分机

extension Encodable {
var dict: [String: Any]? {
guard let data = try? JSONEncoder().encode(self) else { return nil }
return (try? JSONSerialization.jsonObject(with: data, options: .allowFragments)).flatMap { $0 as? [String: Any] }
}
}

然后只更改结构

struct DiscussionMessage: Encodable {
...your properties...
}

代码

let msg = DiscussionMessage(data to populate with)
let dict = msg.dict
messagesReference.childByAutoId().setValue(dict)

请记住，实时数据库没有nil-任何没有值的节点都不存在，因此只会写入有值的属性。

哦，并确保属性是有效的Firebase类型的NSNumber、NSString、NSDictionary和NSArray(和Bool(