[add] audio fadeOut function added

AVPlayerFade.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		78629A462ABB716F00A29C2A /* sample.mp3 in Resources */ = {isa = PBXBuildFile; fileRef = 78629A452ABB716F00A29C2A /* sample.mp3 */; };
 		943BC86A24764A7400249743 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 943BC86924764A7400249743 /* AppDelegate.swift */; };
 		943BC86C24764A7400249743 /* SceneDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 943BC86B24764A7400249743 /* SceneDelegate.swift */; };
 		943BC86E24764A7400249743 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 943BC86D24764A7400249743 /* ViewController.swift */; };
@@ -17,6 +18,7 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		78629A452ABB716F00A29C2A /* sample.mp3 */ = {isa = PBXFileReference; lastKnownFileType = audio.mp3; path = sample.mp3; sourceTree = "<group>"; };
 		943BC86624764A7400249743 /* AVPlayerFade.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = AVPlayerFade.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		943BC86924764A7400249743 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		943BC86B24764A7400249743 /* SceneDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SceneDelegate.swift; sourceTree = "<group>"; };
@@ -62,6 +64,7 @@
 				943BC86B24764A7400249743 /* SceneDelegate.swift */,
 				943BC86D24764A7400249743 /* ViewController.swift */,
 				94BB669C247693EF00B79C21 /* AVPlayerExtensions.swift */,
+				78629A452ABB716F00A29C2A /* sample.mp3 */,
 				943BC86F24764A7400249743 /* Main.storyboard */,
 				943BC87224764A7600249743 /* Assets.xcassets */,
 				943BC87424764A7600249743 /* LaunchScreen.storyboard */,
@@ -130,6 +133,7 @@
 			files = (
 				943BC87624764A7600249743 /* LaunchScreen.storyboard in Resources */,
 				943BC87324764A7600249743 /* Assets.xcassets in Resources */,
+				78629A462ABB716F00A29C2A /* sample.mp3 in Resources */,
 				943BC87124764A7400249743 /* Main.storyboard in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

AVPlayerFade.xcodeproj/xcuserdata/tushar.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Bucket
+   uuid = "4E83AF58-0632-4D15-9E2B-D2E7513F9B20"
+   type = "1"
+   version = "2.0">
+</Bucket>

AVPlayerFade.xcodeproj/xcuserdata/tushar.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>SchemeUserState</key>
+	<dict>
+		<key>AVPlayerFade.xcscheme_^#shared#^_</key>
+		<dict>
+			<key>orderHint</key>
+			<integer>0</integer>
+		</dict>
+	</dict>
+</dict>
+</plist>

AVPlayerFade/AVPlayerExtensions.swift

@@ -17,7 +17,7 @@ extension AVPlayer {
     ///   - duration: duration in seconds for the fade
     ///   - completion: callback indicating completion
     /// - Returns: Timer?
-    func fadeVolume(from: Float, to: Float, duration: Float, completion: (() -> Void)? = nil) -> Timer? {
+    func fadeInVolume(from: Float, to: Float, duration: Float, completion: (() -> Void)? = nil) -> Timer? {
 
         // 1. Set Initial volume
         volume = from
@@ -63,4 +63,48 @@ extension AVPlayer {
             }
         })
     }
+
+    func fadeOutVolume(from: Float, to: Float, duration: Double, completion: (() -> Void)? = nil) -> Timer? {
+
+        volume = from
+        guard from != to else { return nil }
+
+        let interval: Float = 0.1
+        let range = from - to
+        let step = (range*interval) / Float(duration)
+
+        func reachedTarget() -> Bool {
+
+            guard volume >= 0, volume <= 1 else {
+                volume = from
+                return true
+            }
+
+            if from > to {
+                return volume <= to
+            }
+            return volume >= to
+        }
+
+        return Timer.scheduledTimer(withTimeInterval: Double(interval), repeats: true, block: { [weak self] (timer) in
+            guard let self = self else { return }
+
+            DispatchQueue.main.async {
+
+                if !reachedTarget() {
+                    if let currentItem = self.currentItem {
+                        let totalDuration = CMTimeGetSeconds(currentItem.duration)
+                        let currentTime = CMTimeGetSeconds(currentItem.currentTime())
+                        let fadeOutTime = totalDuration - duration
+                        if currentTime >= fadeOutTime {
+                            self.volume -= step
+                        }
+                    }
+                } else {
+                    timer.invalidate()
+                    completion?()
+                }
+            }
+        })
+    }
 }

AVPlayerFade/ViewController.swift

@@ -22,14 +22,16 @@ class ViewController: UIViewController {
 
     private func setupPlayer() {
         // Setup player
-        let url = URL(string: "https://file-examples.com/wp-content/uploads/2017/11/file_example_MP3_700KB.mp3")!
+        guard let url = Bundle.main.url(forResource: "sample", withExtension: "mp3") else { return }
         let item = AVPlayerItem(url: url)
         player.replaceCurrentItem(with: item)
         player.volume = 0
         player.play()
 
         // Fade player volume from 0 to 1 in 5 seconds
-        fadeTimer = player.fadeVolume(from: 0, to: 1, duration: 5)
+        fadeTimer = player.fadeInVolume(from: 0, to: 1, duration: 5)
+        // or
+        // fadeTimer = player.fadeOutVolume(from: 1, to: 0, duration: 5)
     }
 
 }