added ability to query aggregates and attributes straight from the persistent store

HardcoreData/DataStack+Observing.swift

@@ -0,0 +1,50 @@
+//
+//  DataStack+Observing.swift
+//  HardcoreData
+//
+//  Copyright (c) 2015 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+import CoreData
+import GCDKit
+
+
+// MARK: - DataStack
+
+public extension DataStack {
+    
+    // MARK: Public
+    
+    public func observeObjectList<T: NSManagedObject>(entity: T.Type, _ queryClauses: FetchClause...) -> ManagedObjectListController<T> {
+        
+        HardcoreData.assert(GCDQueue.Main.isCurrentExecutionContext(), "Attempted to fetch from a <\(self.dynamicType)> outside the main queue.")
+        
+        // TODO: sectionNameKeyPath and cacheResults
+        return ManagedObjectListController(
+            dataStack: self,
+            entity: entity,
+            sectionNameKeyPath: nil,
+            cacheResults: false,
+            queryClauses: queryClauses
+        )
+    }
+}