From 05d830191c288034f3f97c31ff2a6f76e3653b6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Elvis=20Nu=C3=B1ez?= <elvisnunez@me.com>
Date: Sun, 13 Dec 2015 17:59:31 +0100
Subject: [PATCH] Improve notification example

---
 AppNet/Networking.swift     | 35 +++++++++++++++++++++++++++++------
 AppNet/ViewController.swift | 14 --------------
 2 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/AppNet/Networking.swift b/AppNet/Networking.swift
index fb3abeea..71263787 100644
--- a/AppNet/Networking.swift
+++ b/AppNet/Networking.swift
@@ -2,7 +2,7 @@ import UIKit
 import DATAStack
 import Sync
 
-class Networking {
+class Networking: NSObject {
     let AppNetURL = "https://api.app.net/posts/stream/global"
     let dataStack: DATAStack
 
@@ -24,12 +24,35 @@ class Networking {
         }).resume()
     }
 
+    /*
+    An example on how to properly receive notifications of changes. Includes a local "global.json" so you can modify it to try it,
+    but it can easily work with your own JSON too. Please use notifications to react to changes, not to modify the returned elements
+    since that would be unsafe.
+    */
     func fetchLocalItems(completion: (NSError?) -> Void) {
-        guard let url = NSURL(string: "global.json"), filePath = NSBundle.mainBundle().pathForResource(url.URLByDeletingPathExtension?.absoluteString, ofType: url.pathExtension) else { fatalError() }
-        guard let data = NSData(contentsOfFile: filePath) else { fatalError() }
+        let url = NSURL(string: "global.json")!
+        let filePath = NSBundle.mainBundle().pathForResource(url.URLByDeletingPathExtension?.absoluteString, ofType: url.pathExtension)!
+        let data = NSData(contentsOfFile: filePath)!
         let json = try! NSJSONSerialization.JSONObjectWithData(data, options: []) as! [String: AnyObject]
-        Sync.changes(json["data"] as! Array, inEntityNamed: "Data", dataStack: self.dataStack, completion: { error in
-            completion(error)
-        })
+
+        self.dataStack.performInNewBackgroundContext { backgroundContext in
+            NSNotificationCenter.defaultCenter().addObserver(self, selector: "changeNotification:", name: NSManagedObjectContextObjectsDidChangeNotification, object: backgroundContext)
+
+            Sync.changes(json["data"] as! Array, inEntityNamed: "Data", predicate: nil, parent: nil, inContext: backgroundContext, dataStack: self.dataStack, completion: { error in
+                NSNotificationCenter.defaultCenter().removeObserver(self, name: NSManagedObjectContextObjectsDidChangeNotification, object: nil)
+
+                completion(error)
+            })
+        }
+    }
+
+    func changeNotification(notification: NSNotification) {
+        let updatedObjects = notification.userInfo?[NSUpdatedObjectsKey]
+        let deletedObjects = notification.userInfo?[NSDeletedObjectsKey]
+        let insertedObjects = notification.userInfo?[NSInsertedObjectsKey]
+
+        print("updatedObjects: \(updatedObjects)")
+        print("deletedObjects: \(deletedObjects)")
+        print("insertedObjects: \(insertedObjects)")
     }
 }
diff --git a/AppNet/ViewController.swift b/AppNet/ViewController.swift
index 4813e33b..3e781067 100644
--- a/AppNet/ViewController.swift
+++ b/AppNet/ViewController.swift
@@ -33,20 +33,6 @@ class ViewController: UITableViewController {
 
         fetchCurrentObjects()
         fetchNewData()
-
-        NSNotificationCenter.defaultCenter().addObserver(self, selector: "changeNotification:", name: NSManagedObjectContextObjectsDidChangeNotification, object: self.dataStack.mainContext)
-    }
-
-    // MARK: Private methods
-
-    func changeNotification(notification: NSNotification) {
-        let updatedObjects = notification.userInfo?[NSUpdatedObjectsKey]
-        let deletedObjects = notification.userInfo?[NSDeletedObjectsKey]
-        let insertedObjects = notification.userInfo?[NSInsertedObjectsKey]
-
-        print("updatedObjects: \(updatedObjects)")
-        print("deletedObjects: \(deletedObjects)")
-        print("insertedObjects: \(insertedObjects)")
     }
 
     func fetchNewData() {