从 Firebase Firestore 获取数据时，我的 SwiftUI 应用程序因错误而崩溃。 这可能是由什么引起的？

Question

When I launch the application it does load the data but when it is building a model it crashes with the following error:

The following code is from my GetIphonesData.swift class:

import Foundation
import Firebase
import Combine

class GetIphonesData : ObservableObject {
    @Published var data = [Iphone]()

    init() {
        let db = Firestore.firestore()

        db.collection("iphones").addSnapshotListener { (snap, err) in
            DispatchQueue.main.async {
                if let err = err {
                    print("Error getting documents: \(err)")
                } else {
                    for i in snap!.documents {
                        let iphone = Iphone(id: i.documentID,
                                                name: i.get("name") as! String,
                                                models: i.get("model") as! String,
                                                yearReleased: i.get("yearReleased") as! String,
                                                storageVariants: i.get("storageVariants") as! String,
                                                colors: i.get("colors") as! String,
                                                batteryCapacity: i.get("batteryCapacity") as! String,
                                                cameraResolution: i.get("cameraResolution") as! String,
                                                screenSize: i.get("screenSize") as! String,
                                                screenResolution: i.get("screenResolution") as! String,
                                                sensors: i.get("sensors") as! String,
                                                memory: i.get("memory") as! String)

                        self.data.append(iphone)
                    }
                }
            }
        }
    }
}

When I print the data it prints. When I have 1 item in the database it works but once I add more items into the database it crashes. Is there a fix to this or is there a reason to it at all?

Answer 1

The return value of the below code is nil and hence it's unable to cast it as a string.

models: i.get("model") as! String,

Change the above to:

models: i.get("model") != nil ?? i.get("model") as! String : "",

(or)

models: i.get("model") as? String ?? "",

Hope that helps.