[Objects] Prevent updating when nothing changes

Author: kylef

RxQueryKit/RxQueryKit.swift

@@ -9,9 +9,34 @@ extension QuerySet {
   /// Performs a query for all objects matching the set predicate ordered by any set sort descriptors.
   /// Emits a value with an array of all objects when the managed object context is changed.
   public func objects() throws -> Observable<[ModelType]> {
-    return context.qk_objectsDidChange().map { notification in
-      return try self.array()
-    }.startWith(try self.array())
+    let initial = try self.array()
+
+    return Observable.create { observer in
+      observer.on(.Next(initial))
+
+      return self.context.qk_objectsDidChange().subscribeNext { notification in
+        let insertedObjects = notification.insertedObjects.filter {
+          $0.entity.name == self.entityName
+        }
+        let updatedObjects = notification.updatedObjects.filter {
+          $0.entity.name == self.entityName
+        }
+        let deletedObjects = notification.deletedObjects.filter {
+          $0.entity.name == self.entityName
+        }
+
+        if insertedObjects.isEmpty && updatedObjects.isEmpty && deletedObjects.isEmpty {
+          return
+        }
+
+        do {
+          let objects = try self.array()
+          observer.onNext(objects)
+        } catch {
+          observer.onError(error)
+        }
+      }
+    }
   }
 
   /// Performs a query for the count of all objects matching the set predicate.

RxQueryKitTests/RxQueryKitTests.swift

@@ -52,10 +52,55 @@ class RxQueryKitTests: XCTestCase {
 
     disposable.dispose()
   }
+
+  func testObjects() {
+    var objects: [[Person]] = []
+
+    let disposable = try! Person.queryset(context)
+      .orderBy { $0.name.ascending() }
+      .objects()
+      .subscribeNext {
+        objects.append($0)
+      }
+
+    // Initial value
+    XCTAssertEqual(objects, [[]])
+
+    // Created
+    let p1 = Person.create(context, name: "kyle1")
+    let p2 = Person.create(context, name: "kyle2")
+    let p3 = Person.create(context, name: "kyle3")
+    try! context.save()
+    XCTAssertEqual(objects, [[], [p1, p2, p3]])
+
+    // Deleted
+    context.deleteObject(p1)
+    context.deleteObject(p3)
+    try! context.save()
+    XCTAssertEqual(objects, [[], [p1, p2, p3], [p2]])
+
+    // Modified Object
+    context.deleteObject(p1)
+    context.deleteObject(p3)
+    p2.name = "kyle updated"
+    try! context.save()
+    XCTAssertEqual(objects, [[], [p1, p2, p3], [p2], [p2]])
+
+    // Doesn't update when nothing changes
+    Comment.create(context, text: "Hello World")
+    try! context.save()
+    XCTAssertEqual(objects, [[], [p1, p2, p3], [p2], [p2]])
+
+    disposable.dispose()
+  }
 }
 
 
 @objc(Person) class Person : NSManagedObject {
+  class var name:Attribute<String> {
+    return Attribute("name")
+  }
+
   class func createEntityDescription() -> NSEntityDescription {
     let name = NSAttributeDescription()
     name.name = "name"