Add ManagedObjectViewContext

Author: colemancda

Sources/CoreDataModel/NSManagedObjectContext.swift

@@ -7,10 +7,11 @@
 
 #if canImport(CoreData)
 import Foundation
+import Combine
 import CoreData
 import CoreModel
 
-extension NSManagedObjectContext: ModelStorage, ViewContext {
+extension NSManagedObjectContext: ModelStorage {
 
     public func fetch(_ entity: EntityName, for id: ObjectID) throws -> ModelData? {
         try self.find(entity, for: id)
@@ -58,6 +59,41 @@ extension NSManagedObjectContext: ModelStorage, ViewContext {
     }
 }
 
+@MainActor
+public final class ManagedObjectViewContext: ViewContext, ObservableObject {
+    
+    internal let context: NSManagedObjectContext
+    
+    public init(context: NSManagedObjectContext) {
+        self.context = context
+        assert(context.concurrencyType == .mainQueueConcurrencyType)
+    }
+    
+    public init(persistentContainer: NSPersistentContainer) {
+        self.context = persistentContainer.viewContext
+    }
+    
+    /// Fetch managed object.
+    public func fetch(_ entity: EntityName, for id: ObjectID) throws -> ModelData? {
+        try context.fetch(entity, for: id)
+    }
+    
+    /// Fetch managed objects.
+    public func fetch(_ fetchRequest: FetchRequest) throws -> [ModelData] {
+        try context.fetch(fetchRequest)
+    }
+    
+    /// Fetch managed objects IDs.
+    public func fetchID(_ fetchRequest: FetchRequest) throws -> [ObjectID] {
+        try context.fetchID(fetchRequest)
+    }
+    
+    /// Fetch and return result count.
+    public func count(_ fetchRequest: FetchRequest) throws -> UInt {
+        try context.count(fetchRequest)
+    }
+}
+
 internal extension NSManagedObjectContext {
 
     func fetchObjects(_ fetchRequest: FetchRequest) throws -> [NSManagedObject] {