Addressed opened issue # 1

Sources/Sound.swift

@@ -275,6 +275,22 @@ open class Sound {
             }
         }
     }
+
+    /// Set volume with duration i.e. fade to a new volume over a duration
+    @available(iOS 10.0, *)
+    public func setVolume(_ volume: Float, fadeDuration duration: TimeInterval) {
+        for player in players {
+            player.setVolume(volume, fadeDuration: duration)
+        }
+    }
+
+    /// Current time.
+    /// If the sound is playing, currentTime is the offset of the current playback position, measured in seconds from the start of the sound.
+    public var currentTime: TimeInterval {
+        get {
+            return players[counter].currentTime
+        }
+    }
 
     /// Stop playing sound for given sound file.
     ///
@@ -319,6 +335,10 @@ public protocol Player: class {
 
     /// Resume playing.
     func resume()
+
+    /// Set volume with duration i.e. fade to a new volume over a duration
+    @available(iOS 10.0, *)
+    func setVolume(_ volume: Float, fadeDuration duration: TimeInterval)
 
     /// Prepare the sound.
     func prepareToPlay() -> Bool
@@ -331,6 +351,9 @@ public protocol Player: class {
     /// Duration of the sound.
     var duration: TimeInterval { get }
 
+    /// Current time.
+    var currentTime: TimeInterval { get set }
+
     /// Sound volume.
     var volume: Float { get set }
 

Tests/SwiftySoundTests/SwiftySoundTests.swift

@@ -15,6 +15,7 @@ extension String: Error {}
 final class MockPlayer: Player {
 
     var duration: TimeInterval = 1
+    var currentTime: TimeInterval = 1
     var volume: Float = 1
     var isPlaying: Bool = false
 
@@ -180,10 +181,25 @@ class SwiftySoundTests: XCTestCase {
         }
     }
 
+    func testVolumeWithDuration() {
+        if let url = bundle.url(forResource: "dog", withExtension: "wav"), let sound = Sound(url: url) {
+            sound.setVolume(0.5, fadeDuration: 0)
+            XCTAssertEqual(sound.volume, 0.5)
+            sound.setVolume(0.0, fadeDuration: 0)
+            XCTAssertEqual(sound.volume, 0.0)
+            sound.setVolume(1.0, fadeDuration: 0)
+            XCTAssertEqual(sound.volume, 1.0)
+        }
+    }
+
     func testDuration() {
         XCTAssert(dogSound.duration > 0)
     }
 
+    func testCurrentTime() {
+        XCTAssert(dogSound.currentTime > 0)
+    }
+
     func testNotEnabledPlayback() {
         Sound.enabled = false
         let result = dogSound.play()