HeartButton.swift

import UIKit

class HeartButton: UIButton {
  private var isLiked = false
  
  // ...

  public func flipLikedState() {
    isLiked = !isLiked
    animate()
  }

  private func animate() {
    // Step 1
    UIView.animate(withDuration: 0.1, animations: {
      let newImage = self.isLiked ? self.likedImage : self.unlikedImage
      self.transform = self.transform.scaledBy(x: 0.8, y: 0.8)
      self.setImage(newImage, for: .normal)
    }, completion: { _ in
      // Step 2
      UIView.animate(withDuration: 0.1, animations: {
        self.transform = CGAffineTransform.identity
      })
    })
  }
}