SwipeView.swift

// MARK: - Actions
extension ViewController {
    func swipeView(_ gesture: UIPanGestureRecognizer) {
        guard let subView = gesture.view else { return }
        guard let beginCenter = beginCenter else {
            if gesture.state == .began {
                self.beginCenter = subView.center
            }
            return
        }
        
        let translation = gesture.translation(in: swipeView)
        let centerX = (view.frame.size.width / 2)
        let centerY = (subView.center.y + translation.y)
        let minY = (beginCenter.y)
        let maxY = (beginCenter.y + swipeViewHeight)
        
        if centerY >= minY && centerX <= maxY {
            subView.center = CGPoint(x: centerX,
                                           y: centerY)
        }
        
        if gesture.state == .ended {
            let finalPoint: CGPoint
            if centerY < (beginCenter.y + (swipeViewHeight / 2)) {
                isHidden = false
                bottomConstraint?.constant = 0
                finalPoint = beginCenter
            } else {
                isHidden = true
                bottomConstraint?.constant = -swipeViewHeight
                finalPoint = CGPoint(x: beginCenter.x, y: beginCenter.y + swipeViewHeight)
            }
            
            UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseOut, animations: { 
                subView.center = finalPoint
            }, completion: nil)
        }
        
        gesture.setTranslation(CGPoint(x: 0, y: 0), in: swipeView)
    }
}