onevcat · October 29, 2020 08:48 · Oct 21, 2020 · Oct 21, 2020
diff --git a/TrafficLight.swift b/TrafficLight.swift
@@ -0,0 +1,132 @@
+//: A UIKit based Playground for presenting user interface
+
+import UIKit
+import PlaygroundSupport
+
+public protocol TrafficLightOption {
+    associatedtype Value
+
+    /// 默认的选项值
+    static var defaultValue: Value { get }
+}
+
+extension TrafficLight {
+    public enum GreenLightColor: TrafficLightOption {
+        case green
+        case turquoise
+
+        public static let defaultValue: GreenLightColor = .green
+    }
+}
+
+extension TrafficLight {
+    public var preferredGreenLightColor: TrafficLight.GreenLightColor {
+        get { self[option: GreenLightColor.self] }
+        set { self[option: GreenLightColor.self] = newValue }
+    }
+}
+
+public class TrafficLight {
+
+    public enum State {
+        case stop
+        case proceed
+        case caution
+    }
+
+    private var options = [ObjectIdentifier: Any]()
+
+    public subscript<T: TrafficLightOption>(option type: T.Type) -> T.Value {
+        get {
+            options[ObjectIdentifier(type)] as? T.Value
+                ?? type.defaultValue
+        }
+        set {
+            options[ObjectIdentifier(type)] = newValue
+        }
+    }
+
+    public private(set) var state: State = .stop {
+        didSet { onStateChanged?(state) }
+    }
+
+    public var onStateChanged: ((State) -> Void)?
+
+    public var stopDuration = 4.0
+    public var proceedDuration = 6.0
+    public var cautionDuration = 1.5
+
+    private var timer: Timer?
+
+    public func start() {
+        guard timer == nil else { return }
+        turnState(.stop)
+    }
+
+    public func stop() {
+        timer?.invalidate()
+        timer = nil
+    }
+
+    private func turnState(_ state: State) {
+        switch state {
+        case .proceed:
+            timer = Timer.scheduledTimer(withTimeInterval: proceedDuration, repeats: false) { _ in
+                self.turnState(.caution)
+            }
+        case .caution:
+            timer = Timer.scheduledTimer(withTimeInterval: cautionDuration, repeats: false) { _ in
+                self.turnState(.stop)
+            }
+        case .stop:
+            timer = Timer.scheduledTimer(withTimeInterval: stopDuration, repeats: false) { _ in
+                self.turnState(.proceed)
+            }
+        }
+        self.state = state
+    }
+}
+
+
+class MyViewController : UIViewController {
+
+    var light: TrafficLight!
+
+    override func loadView() {
+        let view = UIView()
+        view.backgroundColor = .white
+        self.view = view
+
+        light = TrafficLight()
+        light.preferredGreenLightColor = .turquoise
+        light.onStateChanged = { [weak self, weak light] state in
+            guard let self = self, let light = light else { return }
+            let color: UIColor
+            switch state {
+            case .proceed: color = light.preferredGreenLightColor.color
+            case .caution: color = .yellow
+            case .stop: color = .red
+            }
+            UIView.animate(withDuration: 0.25) {
+                self.view.backgroundColor = color
+            }
+        }
+        light.start()
+    }
+
+    deinit {
+        light.stop()
+    }
+}
+
+
+extension TrafficLight.GreenLightColor {
+    var color: UIColor {
+        switch self {
+        case .green: return .green
+        case .turquoise: return UIColor(red: 0.25, green: 0.88, blue: 0.82, alpha: 1.00)
+        }
+    }
+}
+// Present the view controller in the Live View window
+PlaygroundPage.current.liveView = MyViewController()