Added Typed NSManagedObjectIDs

Author: RCCoop

README.md

@@ -19,6 +19,7 @@ Helpful tools for Core Data
         - [PersistentHistoryTracker actor](#persistenthistorytracker-actor)
         - [SwiftUI Integration](#swiftui-integration)
 - [CRUD Helpers](#crud-helpers)
+    - [Typed NSManagedObjectID](#typed-nsmanagedobjectid)
     - [Updatable Protocol](#updatable-protocol)
     - [Persistable Protocol](#persistable-protocol)
     - [NSManagedObjectContext Helpers](#nsmanagedobjectcontext-helpers)
@@ -262,6 +263,19 @@ You must set the DataStack into a view's environment using the `dataStackEnviron
 
 # CRUD Helpers
 
+### Typed NSManagedObjectID
+
+Use `TypedObjectID` in place of `NSManagedObjectID` anywhere that you want to enforce type safety around the ID. Because both `NSManagedObjectID` and the `TypedObjectID` wrapper are `Sendable`, they are the best way to send references to `NSManagedObject` between contexts.
+```swift
+let viewContextPerson = Person(...) // get a person on the ViewContext
+let personId = TypedObjectID(viewContextPerson.objectID) // personId refers only to Person type
+
+try backgroundContext.perform {
+    // get a reference to the same Person from storage, but safe for this context:
+    let backgroundContextPerson = try backgroundContext.existingObject(with: personId)
+}
+```
+
 ### Updatable Protocol
 
 Add the `Updatable` protocol to your Model types to get some free functions. Protocol conformance has no requirements except that the implementing type is a `NSManagedObject` subclass.

Sources/RCDataKit/NSExtensions/TypedObjectID.swift

@@ -0,0 +1,25 @@
+//
+//  TypedObjectID.swift
+//  RCDataKit
+//
+//  Created by Ryan Linn on 11/24/24.
+//
+
+import CoreData
+
+/// A wrapper around `NSManagedObjectID` that includes the `NSManagedObject` class type for Swift
+/// type safety.
+public struct TypedObjectID<T: NSManagedObject>: Sendable, Hashable {
+    public let wrapped: NSManagedObjectID
+    
+    public init(_ object: T) {
+        wrapped = object.objectID
+    }
+}
+
+extension NSManagedObjectContext {
+    /// Gets an existing object from the context using a `TypedObjectID`.
+    public func existingObject<T: NSManagedObject>(with typedId: TypedObjectID<T>) throws -> T {
+        try existing(T.self, withID: typedId.wrapped)
+    }
+}