Converting Firebase Datasnapshot to codable JSON data

问题

I am using Firebase Database and am attempting to retrieve and use data using NSObject. I am receiving a NSUnknownKeyException error when running the app causing it to crash.

NSObject:

class WatchList: NSObject {

var filmid: Int?

}

Firebase Code:

ref.child("users").child(uid!).child("watchlist").observe(DataEventType.childAdded, with: { (info) in

            print(info)

            if let dict = info.value as? [String: AnyObject] {
                let list = WatchList()
                list.setValuesForKeys(dict)
                print(list)
            }

    }, withCancel: nil)

I am not sure of what could cause this.

Also to enhance this solution is their a way to take this data and instead of using NSObject I could use Codable and JSONDecoder with the Firebase data?

回答1:

A really nice library to use here is Codable Firebase which I am also using in my project. Just make your class / struct conform to Codable protocol and use FirebaseDecoder to decode your Firebase data into a Swift object.

Example:

Database.database().reference().child("model").observeSingleEvent(of: .value, with: { snapshot in
    guard let value = snapshot.value else { return }
    do {
        let model = try FirebaseDecoder().decode(Model.self, from: value)
        print(model)
    } catch let error {
        print(error)
    }
})

回答2:

You can simply use JSONSerialization to convert the snapshot value property from Any to Data:

let data = try? JSONSerialization.data(withJSONObject: snapshot.value)

You can also extend Firebase DataSnapshot type and add a data and json string properties to it:

import Firebase 

extension DataSnapshot {
    var data: Data? {
        guard let value = value, !(value is NSNull) else { return nil }
        return try? JSONSerialization.data(withJSONObject: value)
    }
    var json: String? { data?.string }
}
extension Data {
    var string: String? { String(data: self, encoding: .utf8) }
}

usage:

guard let data = snapshot.data else { return }

来源：https://stackoverflow.com/questions/53565519/converting-firebase-datasnapshot-to-codable-json-data

标签

json

swift

firebase

codable