Observable property wrapper

Hanson.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		857451EC235A360500473D97 /* ObservablePropertyWrapperTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 857451EB235A360400473D97 /* ObservablePropertyWrapperTests.swift */; };
 		C8237A5C1ED82978003279DB /* NotificationObservable.swift in Sources */ = {isa = PBXBuildFile; fileRef = C8237A5B1ED82978003279DB /* NotificationObservable.swift */; };
 		C8237A5E1ED82BBA003279DB /* NotificationObservableTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C8237A5D1ED82BBA003279DB /* NotificationObservableTests.swift */; };
 		C8888E841E9CCA7C00803644 /* Bindable.swift in Sources */ = {isa = PBXBuildFile; fileRef = C8888E741E9CCA7C00803644 /* Bindable.swift */; };
@@ -43,6 +44,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		857451EB235A360400473D97 /* ObservablePropertyWrapperTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ObservablePropertyWrapperTests.swift; sourceTree = "<group>"; };
 		C8237A5B1ED82978003279DB /* NotificationObservable.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NotificationObservable.swift; sourceTree = "<group>"; };
 		C8237A5D1ED82BBA003279DB /* NotificationObservableTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NotificationObservableTests.swift; sourceTree = "<group>"; };
 		C8888E741E9CCA7C00803644 /* Bindable.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Bindable.swift; sourceTree = "<group>"; };
@@ -174,12 +176,13 @@
 			isa = PBXGroup;
 			children = (
 				C8DBC7601E3A4E2E0028E936 /* Helpers */,
-				C8DBC7541E3A4E170028E936 /* ObservationManagerTests.swift */,
-				C8DBC7531E3A4E170028E936 /* EventPublisherTests.swift */,
-				C8DBC7551E3A4E170028E936 /* ObservableTests.swift */,
+				C8EB01DB1E435A0F0036E3C9 /* CustomBindableTests.swift */,
 				C8DBC7521E3A4E170028E936 /* DynamicObservableTests.swift */,
+				C8DBC7531E3A4E170028E936 /* EventPublisherTests.swift */,
 				C8237A5D1ED82BBA003279DB /* NotificationObservableTests.swift */,
-				C8EB01DB1E435A0F0036E3C9 /* CustomBindableTests.swift */,
+				857451EB235A360400473D97 /* ObservablePropertyWrapperTests.swift */,
+				C8DBC7551E3A4E170028E936 /* ObservableTests.swift */,
+				C8DBC7541E3A4E170028E936 /* ObservationManagerTests.swift */,
 				C8DBC72B1E3A47370028E936 /* Info.plist */,
 			);
 			path = HansonTests;
@@ -335,6 +338,7 @@
 				C8DBC7641E3A4E2E0028E936 /* TestEventPublisher.swift in Sources */,
 				C8DBC75B1E3A4E170028E936 /* ObservationManagerTests.swift in Sources */,
 				C8DBC7631E3A4E2E0028E936 /* TestObject.swift in Sources */,
+				857451EC235A360500473D97 /* ObservablePropertyWrapperTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Hanson/Observable/Observable.swift

@@ -10,6 +10,7 @@ import Foundation
 
 /// The `Observable` class represents a value that can be observed for changes.
 /// When changing the observable's value, the observable will publish a `ValueChange` event with the old and new value.
+@propertyWrapper
 public class Observable<Value>: EventPublisher, Bindable {
 
     /// An alias for the event type that the observable publishes.
@@ -22,8 +23,22 @@ public class Observable<Value>: EventPublisher, Bindable {
         _value = value
     }
 
+    /// Initializes the observable through a propertyWrapper's initial value assignment.
+    ///
+    /// - Parameter value: The observable's initial value.
+    public init(wrappedValue value: Value) {
+        _value = value
+    }
+
     // MARK: Value
 
+    /// The wrapped value of the observable as accessed through the propertyWrapper.
+    /// When setting this to a new value, the observable will publish a `ValueChange` event with the old and new value.
+    public var wrappedValue: Value {
+        get { return value }
+        set { value = newValue }
+    }
+
     /// The value of the observable. When setting this to a new value, the observable will publish a `ValueChange` event with the old and new value.
     public var value: Value {
         get {

HansonTests/ObservablePropertyWrapperTests.swift

@@ -0,0 +1,71 @@
+//
+//  ObservablePropertyWrapperTests.swift
+//  HansonTests
+//
+//  Created by Niklas Holloh on 26.07.19.
+//  Copyright © 2019 Blendle. All rights reserved.
+//
+
+import XCTest
+@testable import Hanson
+
+class ObservablePropertyWrapperTests: XCTestCase {
+
+    @Observable var value = "Hello World"
+
+    func testObservingValue() {
+        var lastEvent: ValueChange<String>!
+        _value.addEventHandler { event in
+            lastEvent = event
+        }
+
+        // Verify that changing the value publishes an event with the old and new value.
+        value = "New Value"
+        XCTAssertEqual(lastEvent.oldValue, "Hello World")
+        XCTAssertEqual(lastEvent.newValue, "New Value")
+
+        value = "Some Other Value"
+        XCTAssertEqual(lastEvent.oldValue, "New Value")
+        XCTAssertEqual(lastEvent.newValue, "Some Other Value")
+    }
+
+    func testSilentlyUpdatingValue() {
+        var lastEvent: ValueChange<String>!
+        _value.addEventHandler { event in
+            lastEvent = event
+        }
+
+        // Verify that changing the value works via the silently update function.
+        _value.silentlyUpdateValue(to: "New Value")
+        XCTAssertEqual(value, "New Value")
+
+        // Verify that no event has been published.
+        XCTAssertNil(lastEvent)
+
+    }
+
+    func testUpdatingValueOnMultipleQueues() {
+        var numberOfEvents = 0
+        _value.addEventHandler { _ in
+            numberOfEvents += 1
+        }
+
+        // Update the value 100 times on different queues.
+        for i in 0..<100 {
+            let valueExpectation = expectation(description: "Updated value")
+
+            let queue = DispatchQueue(label: "com.blendle.hanson.tests.observable.queue\(i)")
+            queue.async {
+                self.value = "New Value"
+
+                valueExpectation.fulfill()
+            }
+        }
+
+        waitForExpectations(timeout: 10, handler: nil)
+
+        // Verify that the value has been updated 100 times.
+        XCTAssertEqual(numberOfEvents, 100)
+    }
+
+}