iOS开发：Realm数据模型为何需required初始化器及解决办法

Hey there! I see you're running into an issue converting your Firebase model to a Realm Object subclass—let's break down what's going on and fix it step by step.

Why the Error Occurs #

Realm's Object class enforces that all subclasses provide a no-argument init() initializer because Realm relies on this internally to create instances when loading data from the database. When you define custom designated initializers (like your init(name:coordinate:) and init(dictionary:)), Swift automatically removes the default no-argument initializer inherited from Object. Even if you used Xcode's auto-fix, you might have missed a critical detail: the initializer needs to be marked required and must call super.init() to properly initialize the parent Object class.

I also spotted two typos in your code that would cause extra errors:

• Geopoint should be GeoPoint (capital 'P'—Firebase's location type is spelled GeoPoint)
• Longitude in your default coordinate should be longitude (lowercase 'l'—the parameter name is case-sensitive)

Fixed Code Implementation #

Here's the corrected version of your CityKM class that resolves all issues:

import Foundation
import FirebaseFirestore
import RealmSwift

class CityKM: Object {
    @objc dynamic var name: String = ""
    @objc dynamic var coordinate: GeoPoint = GeoPoint(latitude: 6.01212, longitude: -101.212)
    
    // Required no-argument initializer for Realm
    required init() {
        super.init()
    }
    
    init(name: String, coordinate: GeoPoint) {
        super.init()
        self.name = name
        self.coordinate = coordinate
    }
    
    init(dictionary: [String: Any]) {
        super.init()
        // Use optional binding instead of force-unwrapping to avoid crashes
        if let nameValue = dictionary["name"] as? String {
            self.name = nameValue
        }
        if let coordinateValue = dictionary["coordinate"] as? GeoPoint {
            self.coordinate = coordinateValue
        }
    }
    
    // Optional: Define a primary key if you want Realm to uniquely identify objects
    override class func primaryKey() -> String? {
        return "name"
    }
}

Key Changes Explained #

1. Added required init(): This satisfies Realm's mandatory requirement for a no-argument initializer. Calling super.init() ensures the parent Object class is properly initialized.
2. Corrected typos: Fixed the case issues with GeoPoint and longitude to match Firebase's API specifications.
3. Safer dictionary initialization: Replaced risky force-unwraps (as!) with optional binding (as?) to prevent crashes if Firebase returns missing or incorrectly formatted data.
4. Optional primary key: Added an override for primaryKey() (optional but useful) to help Realm track unique objects, which simplifies updates and avoids duplicates.

Why Xcode's Auto-Fix Might Have Failed #

If you used Xcode's "Fix" suggestion, it likely added a required init() without including super.init(). This is invalid because Object's initializer must be invoked to set up the Realm object properly—our fixed version includes this critical call.

内容的提问来源于stack exchange，提问作者Agung