Syntactically-clean and portable SwiftUI bindings for optional properties on CoreData entities.

NSManagedObject+DynamicBindings.swift

//
//  NSManagedObject+DynamicBindings.swift
//
//  Created by Stephan Casas on 3/31/24.
//

import SwiftUI;
import CoreData;

protocol DynamicBindings: NSManagedObject { }

extension DynamicBindings {
    
    /// Create a SwiftUI binding for a managed object's optional property
    /// - Parameters:
    ///   - key: The keypath to the binding's mutable property.
    ///   - defaultValue: The default value provided to the binding if no value is present.
    func binding<T>(
        for key: ReferenceWritableKeyPath<Self, T?>,
        defaultValue: T? = nil
    ) -> Binding<T> {
        let defaultValue = defaultValue ?? {
            switch T.self {
            case is String.Type:
                return "" as! T;
            case is Int.Type:
                return 0 as! T;
            case is Bool.Type:
                return false as! T;
            case is Float.Type:
                return Float(0.0) as! T;
            case is Double.Type:
                return Double(0.0) as! T;
            default:
                fatalError("No inferred default value declared for type \(T.self). Provide a value to `defaultValue`.");
                break
            }
        }();
        
        return .init(get: {
            self[keyPath: key] ?? defaultValue
        }, set: {
            self[keyPath: key] = $0;
        });
    }
    
}

Apply the protocol to your CoreData entity using an extension:

extension Item: DynamicBindings { }

Then use the utility in your SwiftUI views:

struct ItemEditorView: View {

  @ObservedObject private var item: Item;
  
  init(_ item: Item) {
    self.item = item;
  }

  var body: some View {
    TextField("Title", text: self.item.binding(for: \.title))
  }

}