Delayed animation cancellation (#231)

Author: mfikes

Impedance Converter/Impedance Converter/SmoothAnimation.swift

@@ -6,23 +6,26 @@ class SmoothAnimation {
     private var animationTimer: Timer?
     private var currentInterpolator: Double
     private var updateAction: ((Double) -> Void)?
+    private var delayWorkItem: DispatchWorkItem?
 
     init(initialValue: Double = 0) {
         self.currentInterpolator = initialValue
     }
 
     func startAnimating(target: Double, totalAnimationTime: Double = 0.25, delay: TimeInterval = 0, updateAction: @escaping (Double) -> Void) {
 
-        // Invalidate existing timer before starting a new animation
-        animationTimer?.invalidate()
+        // Stop existing animation before starting a new one
+        stopAnimating()
 
         if SmoothAnimation.isAnimationDisabled {
             self.currentInterpolator = target
             updateAction(target)
             return
         }
 
-        DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
+        let workItem = DispatchWorkItem { [weak self] in
+            guard let self = self else { return }
+
             self.updateAction = updateAction
             self.animationTimer?.invalidate()
             let startValue = self.currentInterpolator
@@ -47,19 +50,20 @@ class SmoothAnimation {
                 self.updateAction?(interpolatorValue)
             }
         }
+
+        self.delayWorkItem = workItem
+        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: workItem)
     }
 
     func startAnimating(from: Double, target: Double, totalAnimationTime: Double = 0.25, delay: TimeInterval = 0, updateAction: @escaping (Double) -> Void) {
-        // Invalidate existing timer before starting a new animation
-        animationTimer?.invalidate()
+        // Stop existing animation before starting a new one
+        stopAnimating()
         self.currentInterpolator = from
-
-        DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
-            self.startAnimating(target: target, totalAnimationTime: totalAnimationTime, updateAction: updateAction)
-        }
+        startAnimating(target: target, totalAnimationTime: totalAnimationTime, delay: delay, updateAction: updateAction)
     }
 
     func stopAnimating() {
         animationTimer?.invalidate()
+        delayWorkItem?.cancel()
     }
 }