Migrate the source code to Swift 4

.swift-version

@@ -1 +1 @@
-3.0
+4.0

Cartfile.resolved

@@ -1,3 +1,3 @@
 github "Quick/Nimble" "v7.0.2"
 github "Quick/Quick" "v1.2.0"
-github "vadymmarkov/Pitchy" "2.0.1"
+github "vadymmarkov/Pitchy" "3.0.0"

Source/Estimation/EstimationFactory.swift

@@ -1,6 +1,5 @@
-struct EstimationFactory {
-
-  static func create(_ strategy: EstimationStrategy) -> Estimator {
+final class EstimationFactory {
+  func create(_ strategy: EstimationStrategy) -> Estimator {
     let estimator: Estimator
 
     switch strategy {

Source/Estimation/Estimator.swift

@@ -1,20 +1,16 @@
 protocol Estimator {
   var transformer: Transformer { get }
-
   func estimateFrequency(sampleRate: Float, buffer: Buffer) throws -> Float
   func estimateFrequency(sampleRate: Float, location: Int, bufferCount: Int) -> Float
 }
 
-extension Estimator {
-
-  // MARK: - Default implementation
+// MARK: - Default implementations
 
+extension Estimator {
   func estimateFrequency(sampleRate: Float, location: Int, bufferCount: Int) -> Float {
     return Float(location) * sampleRate / (Float(bufferCount) * 2)
   }
 
-  // MARK: - Helpers
-
   func maxBufferIndex(from buffer: [Float]) throws -> Int {
     guard buffer.count > 0 else {
       throw EstimationError.emptyBuffer

Source/Estimation/LocationEstimator.swift

@@ -2,10 +2,9 @@ protocol LocationEstimator: Estimator {
   func estimateLocation(buffer: Buffer) throws -> Int
 }
 
-extension LocationEstimator {
-
-  // MARK: - Default implementation
+// MARK: - Default implementation
 
+extension LocationEstimator {
   var transformer: Transformer {
     return FFTTransformer()
   }

Source/Estimation/Strategies/BarycentricEstimator.swift

@@ -1,7 +1,6 @@
 import Foundation
 
-struct BarycentricEstimator: LocationEstimator {
-
+final class BarycentricEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     let elements = buffer.elements
     let maxIndex = try maxBufferIndex(from: elements)

Source/Estimation/Strategies/HPSEstimator.swift

@@ -1,7 +1,6 @@
-struct HPSEstimator: LocationEstimator {
-
-  let harmonics = 5
-  let minIndex = 20
+final class HPSEstimator: LocationEstimator {
+  private let harmonics = 5
+  private let minIndex = 20
 
   func estimateLocation(buffer: Buffer) throws -> Int {
     var spectrum = buffer.elements

Source/Estimation/Strategies/JainsEstimator.swift

@@ -1,7 +1,6 @@
 import Foundation
 
-struct JainsEstimator: LocationEstimator {
-
+final class JainsEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     let elements = buffer.elements
     let maxIndex = try maxBufferIndex(from: elements)

Source/Estimation/Strategies/MaxValueEstimator.swift

@@ -1,5 +1,4 @@
-struct MaxValueEstimator: LocationEstimator {
-
+final class MaxValueEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     return try maxBufferIndex(from: buffer.elements)
   }

Source/Estimation/Strategies/QuadradicEstimator.swift

@@ -1,7 +1,6 @@
 import Foundation
 
-struct QuadradicEstimator: LocationEstimator {
-
+final class QuadradicEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     let elements = buffer.elements
     let maxIndex = try maxBufferIndex(from: elements)

Source/Estimation/Strategies/QuinnsFirstEstimator.swift

@@ -1,7 +1,6 @@
 import Foundation
 
-struct QuinnsFirstEstimator: LocationEstimator {
-
+final class QuinnsFirstEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     let elements = buffer.elements
     let maxIndex = try maxBufferIndex(from: elements)

Source/Estimation/Strategies/QuinnsSecondEstimator.swift

@@ -1,7 +1,6 @@
 import Foundation
 
-struct QuinnsSecondEstimator: LocationEstimator {
-
+final class QuinnsSecondEstimator: LocationEstimator {
   func estimateLocation(buffer: Buffer) throws -> Int {
     let elements = buffer.elements
     let maxIndex = try maxBufferIndex(from: elements)
@@ -27,7 +26,7 @@ struct QuinnsSecondEstimator: LocationEstimator {
     return sanitize(location: location, reserveLocation: maxIndex, elements: elements)
   }
 
-  func tau(_ x: Float) -> Float {
+  private func tau(_ x: Float) -> Float {
     let p1 = log(3 * pow(x, 2.0) + 6 * x + 1)
     let part1 = x + 1 - sqrt(2/3)
     let part2 = x + 1 + sqrt(2/3)

Source/Estimation/Strategies/YINEstimator.swift

@@ -8,8 +8,7 @@
 
 import UIKit
 
-struct YINEstimator: Estimator {
-
+final class YINEstimator: Estimator {
   let transformer: Transformer = YINTransformer()
   let threshold: Float = 0.05
 

Source/Library/Buffer.swift

@@ -1,5 +1,4 @@
 struct Buffer {
-
   var elements: [Float]
   var realElements: [Float]?
   var imagElements: [Float]?

Source/Library/Extensions/Array+Extensions.swift

@@ -1,5 +1,4 @@
 extension Array where Element:Comparable {
-
   static func fromUnsafePointer(_ data: UnsafePointer<Element>, count: Int) -> [Element] {
     let buffer = UnsafeBufferPointer(start: data, count: count)
     return Array(buffer)

Source/Library/YINUtil.swift

@@ -56,6 +56,7 @@ final class YINUtil {
   // https://code.soundsoftware.ac.uk/projects/pyin/repository but I don't know what
   //
   // Kept for reference only.
+  // swiftlint:disable function_body_length
   class func difference_broken_do_not_use(buffer: [Float]) -> [Float] {
     let frameSize = buffer.count
     let yinBufferSize = frameSize / 2

Source/PitchEngine.swift

@@ -8,18 +8,18 @@ public protocol PitchEngineDelegate: class {
   func pitchEngineWentBelowLevelThreshold(_ pitchEngine: PitchEngine)
 }
 
-public enum PitchEngineError: Error {
-  case recordPermissionDenied
-}
-
 public final class PitchEngine {
+  public enum Error: Swift.Error {
+    case recordPermissionDenied
+  }
+
   public let bufferSize: AVAudioFrameCount
-  public var active = false
+  public private(set) var active = false
   public weak var delegate: PitchEngineDelegate?
 
-  private var estimator: Estimator
-  private var signalTracker: SignalTracker
-  private var queue: DispatchQueue
+  private let estimator: Estimator
+  private let signalTracker: SignalTracker
+  private let queue: DispatchQueue
 
   public var mode: SignalTrackerMode {
     return signalTracker.mode
@@ -44,7 +44,9 @@ public final class PitchEngine {
               signalTracker: SignalTracker? = nil,
               delegate: PitchEngineDelegate? = nil) {
     bufferSize = config.bufferSize
-    estimator = EstimationFactory.create(config.estimationStrategy)
+
+    let factory = EstimationFactory()
+    estimator = factory.create(config.estimationStrategy)
 
     if let signalTracker = signalTracker {
       self.signalTracker = signalTracker
@@ -56,7 +58,7 @@ public final class PitchEngine {
       }
     }
 
-    queue = DispatchQueue(label: "BeethovenQueue", attributes: [])
+    self.queue = DispatchQueue(label: "BeethovenQueue", attributes: [])
     self.signalTracker.delegate = self
     self.delegate = delegate
   }
@@ -85,8 +87,10 @@ public final class PitchEngine {
         guard let weakSelf = self else { return }
 
         guard granted else {
-          weakSelf.delegate?.pitchEngineDidReceiveError(weakSelf,
-            error: PitchEngineError.recordPermissionDenied as Error)
+          weakSelf.delegate?.pitchEngineDidReceiveError(
+            weakSelf,
+            error: Error.recordPermissionDenied
+          )
           return
         }
 
@@ -115,7 +119,6 @@ public final class PitchEngine {
 // MARK: - SignalTrackingDelegate
 
 extension PitchEngine: SignalTrackerDelegate {
-
   public func signalTracker(_ signalTracker: SignalTracker,
                             didReceiveBuffer buffer: AVAudioPCMBuffer,
                             atTime time: AVAudioTime) {

Source/SignalTracking/Units/InputSignalTracker.swift

@@ -4,17 +4,16 @@ public enum InputSignalTrackerError: Error {
   case inputNodeMissing
 }
 
-class InputSignalTracker: SignalTracker {
-
+final class InputSignalTracker: SignalTracker {
   weak var delegate: SignalTrackerDelegate?
   var levelThreshold: Float?
 
-  fileprivate let bufferSize: AVAudioFrameCount
-  fileprivate var audioChannel: AVCaptureAudioChannel?
-  fileprivate let captureSession = AVCaptureSession()
-  fileprivate var audioEngine: AVAudioEngine?
-  fileprivate let session = AVAudioSession.sharedInstance()
-  fileprivate let bus = 0
+  private let bufferSize: AVAudioFrameCount
+  private var audioChannel: AVCaptureAudioChannel?
+  private let captureSession = AVCaptureSession()
+  private var audioEngine: AVAudioEngine?
+  private let session = AVAudioSession.sharedInstance()
+  private let bus = 0
 
   var peakLevel: Float? {
     return audioChannel?.peakHoldLevel
@@ -34,7 +33,6 @@ class InputSignalTracker: SignalTracker {
                 delegate: SignalTrackerDelegate? = nil) {
     self.bufferSize = bufferSize
     self.delegate = delegate
-
     setupAudio()
   }
 
@@ -84,7 +82,7 @@ class InputSignalTracker: SignalTracker {
     captureSession.stopRunning()
   }
 
-  fileprivate func setupAudio() {
+  private func setupAudio() {
     do {
       let audioDevice = AVCaptureDevice.default(for: AVMediaType.audio)
       let audioCaptureInput = try AVCaptureDeviceInput(device: audioDevice!)

Source/SignalTracking/Units/OutputSignalTracker.swift

@@ -1,16 +1,14 @@
 import AVFoundation
 
-class OutputSignalTracker: SignalTracker {
-
+final class OutputSignalTracker: SignalTracker {
   weak var delegate: SignalTrackerDelegate?
   var levelThreshold: Float?
 
-  fileprivate let bufferSize: AVAudioFrameCount
-  fileprivate let audioUrl: URL
-
-  fileprivate var audioEngine: AVAudioEngine!
-  fileprivate var audioPlayer: AVAudioPlayerNode!
-  fileprivate let bus = 0
+  private let bufferSize: AVAudioFrameCount
+  private let audioUrl: URL
+  private var audioEngine: AVAudioEngine!
+  private var audioPlayer: AVAudioPlayerNode!
+  private let bus = 0
 
   var peakLevel: Float? {
     return 0.0

Source/SignalTracking/Units/SimulatorSignalTracker.swift

@@ -29,23 +29,18 @@ import AVFoundation
  * #endif
  *
  */
-public class SimulatorSignalTracker: SignalTracker {
+public final class SimulatorSignalTracker: SignalTracker {
+  private static let sampleRate = 8000.0
+  private static let sampleCount = 1024
 
   public var mode: SignalTrackerMode = .record
-
   public var levelThreshold: Float?
-
   public var peakLevel: Float?
-
   public var averageLevel: Float?
-
   public weak var delegate: SignalTrackerDelegate?
 
-  private var frequencies: [Double]?
-  private var delay: Int
-
-  private static let sampleRate = 8000.0
-  private static let sampleCount = 1024
+  private let frequencies: [Double]?
+  private let delay: Int
 
   public init(delegate: SignalTrackerDelegate? = nil, frequencies: [Double]? = nil, delayMs: Int = 0) {
     self.delegate = delegate
@@ -57,34 +52,37 @@ public class SimulatorSignalTracker: SignalTracker {
     guard let frequencies = self.frequencies else { return }
 
     let time = AVAudioTime(sampleTime: 0, atRate: SimulatorSignalTracker.sampleRate)
-
     var i = 0
 
     for frequency in frequencies {
       let buffer = createPCMBuffer(frequency)
+
       if i == 0 {
         DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(50), execute: {
           self.delegate?.signalTracker(self, didReceiveBuffer: buffer, atTime: time)
         })
-
       } else {
         DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(delay * i), execute: {
           self.delegate?.signalTracker(self, didReceiveBuffer: buffer, atTime: time)
         })
       }
+
       i += 1
     }
+
     DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(delay * i), execute: {
       self.delegate?.signalTrackerWentBelowLevelThreshold(self)
     })
   }
 
-  public func stop() {
-  }
+  public func stop() {}
 
   private func createPCMBuffer(_ frequency: Double) -> AVAudioPCMBuffer {
     let format = AVAudioFormat(standardFormatWithSampleRate: SimulatorSignalTracker.sampleRate, channels: 1)
-    let buffer = AVAudioPCMBuffer(pcmFormat: format!, frameCapacity: AVAudioFrameCount(SimulatorSignalTracker.sampleCount))
+    let buffer = AVAudioPCMBuffer(
+      pcmFormat: format!,
+      frameCapacity: AVAudioFrameCount(SimulatorSignalTracker.sampleCount)
+    )
 
     if let channelData = buffer?.floatChannelData {
       let velocity = Float32(2.0 * .pi * frequency / SimulatorSignalTracker.sampleRate)

Source/Transform/Strategies/FFTTransformer.swift

@@ -1,8 +1,7 @@
 import AVFoundation
 import Accelerate
 
-struct FFTTransformer: Transformer {
-
+final class FFTTransformer: Transformer {
   func transform(buffer: AVAudioPCMBuffer) throws -> Buffer {
     let frameCount = buffer.frameLength
     let log2n = UInt(round(log2(Double(frameCount))))
@@ -46,7 +45,7 @@ struct FFTTransformer: Transformer {
 
   // MARK: - Helpers
 
-  func sqrtq(_ x: [Float]) -> [Float] {
+  private func sqrtq(_ x: [Float]) -> [Float] {
     var results = [Float](repeating: 0.0, count: x.count)
     vvsqrtf(&results, x, [Int32(x.count)])
 

Source/Transform/Strategies/SimpleTransformer.swift

@@ -1,6 +1,6 @@
 import AVFoundation
 
-struct SimpleTransformer: Transformer {
+final class SimpleTransformer: Transformer {
   enum SimpleTransformerError: Error {
     case floatChannelDataIsNil
   }