Add Combine-based Core Data resolver

Sources/_CoreDataDependency/CoreDataCombineObjectResolver.swift

@@ -0,0 +1,70 @@
+//
+//  CoreDataCombineObjectResolver.swift
+//  swift-dependencies-additions
+//
+//  Created by Robert Nash on 12/09/2025.
+//
+
+import CoreData
+import Combine
+
+/// Resolves Core Data objects from their `NSManagedObjectID`s and publishes updates.
+public final class CoreDataCombineObjectResolver<T: NSManagedObject> {
+
+    private let idsSubject = CurrentValueSubject<[NSManagedObjectID], Never>([])
+    public let publisher: AnyPublisher<[T], Never>
+
+    private let context: NSManagedObjectContext
+    private var cancellables = Set<AnyCancellable>()
+
+    public init(
+        context: NSManagedObjectContext,
+        deliverOn: DispatchQueue = .main,
+        debounce: DispatchQueue.SchedulerTimeType.Stride? = nil,
+        sortDescriptors: [NSSortDescriptor]? = nil
+    ) {
+        self.context = context
+
+        var publisher: AnyPublisher<[NSManagedObjectID], Never> = idsSubject
+            .removeDuplicates(by: { lhs, rhs in
+                lhs.count == rhs.count && lhs.elementsEqual(rhs, by: { $0 == $1 })
+            })
+            .eraseToAnyPublisher()
+
+        if let d = debounce {
+            publisher = publisher
+                .debounce(for: d, scheduler: deliverOn)
+                .eraseToAnyPublisher()
+        }
+
+        self.publisher = publisher
+            .flatMap { ids -> AnyPublisher<[T], Never> in
+                Deferred {
+                    Future { promise in
+                        context.perform {
+                            do {
+                                guard let entityName = T.entity().name else {
+                                    promise(.success([])); return
+                                }
+                                let request = NSFetchRequest<T>(entityName: entityName)
+                                request.predicate = NSPredicate(format: "SELF IN %@", Array(ids))
+                                request.sortDescriptors = sortDescriptors
+
+                                let results = try context.fetch(request)
+                                promise(.success(results))
+                            } catch {
+                                promise(.success([]))
+                            }
+                        }
+                    }
+                }
+                .eraseToAnyPublisher()
+            }
+            .receive(on: deliverOn)
+            .eraseToAnyPublisher()
+    }
+
+    public func resolve(_ ids: [NSManagedObjectID]) {
+        idsSubject.send(ids)
+    }
+}