Swift 将 Decodable 结构转换为 Dictionary

Question

我创建了一个可分解的结构，用于解析存储在 firebase 中的数据。

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?
}

我也想使用这个结构在 firebase 中存储数据。但我得到错误：

*** Terminating app due to uncaught exception 'InvalidFirebaseData', reason: '(setValue:) Cannot store object of type __SwiftValue at . Can only store objects of type NSNumber, NSString, NSDictionary, and NSArray.' terminating with uncaught exception of type NSException

当我这样存储数据时：

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)

有没有办法将可解码对象转换为字典以便我可以将其存储在 firebase 中？

Answer 1

你不需要它是可解码的。您需要的是能够对其进行编码（Encodable）。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) }
}

我还将 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: "email@address.com", 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":"email@address.com","question":"question","messageTimestamp":1610557474.2272739,"userCountryCode":"BRA"}
    
    let dictionary = try message.dictionary()
    print(dictionary)  // ["userName": userName, "userEmailAddress": email@address.com, "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: "email@address.com", messageTimestamp: 1610557474.227274, fcmToken: Optional("fcmToken"), question: Optional("question"), recordingUrl: nil)
} catch {
    print(error)
}

Answer 2

我要抛出一个答案，看看是否有帮助。

我建议扩展 Encodable 以允许任何符合 return 自身字典的对象可以写入 Firebase。

这是扩展名

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 { [=10=] as? [String: Any] }
    }
}

然后只需更改结构

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

和代码

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，因此只会写入具有值的属性。

哦 - 并确保属性是 NSNumber、NSString、NSDictionary 和 NSArray（和 Bool）的有效 Firebase 类型

Swift 将 Decodable 结构转换为 Dictionary

Swift converting Decodable struct to Dictionary

swift

firebase

firebase-realtime-database

struct

decodable