Stateful Gesture Recognizer subclass

PanSelectGestureRecognizer

//
//  PanSelectGestureRecognizer.swift
//
//  Created by Garo Hussenjian on 6/24/15.
//
//

import UIKit
import UIKit.UIGestureRecognizerSubclass

class PanSelectGestureRecognizer: UIGestureRecognizer {

    var selectionState: Bool?

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesBegan(touches, withEvent:event);
        if state == .Possible {
            state = .Began;
        }
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesMoved(touches, withEvent: event)
        state = .Changed
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesEnded(touches, withEvent: event)
        state = .Ended
    }

    override func touchesCancelled(touches: Set<UITouch>, withEvent event: UIEvent) {
        super.touchesCancelled(touches, withEvent: event)
        state = .Cancelled
    }
}

Here's how this is integrated at the callback site:

func panSelectGestureRecognized(sender: PanSelectGestureRecognizer) {
        if let pulseView = hitTest(sender.locationInView(self), withEvent: nil) as? PulseView {
            switch sender.state {
            case .Possible, .Began:
                sender.selectionState = !pulseView.selected
                sender.selectionState! ? selectPulseView(pulseView) : deselectPulseView(pulseView)

            case .Changed:
                if pulseView.selected != sender.selectionState {
                    sender.selectionState! ? selectPulseView(pulseView) : deselectPulseView(pulseView)
                }

            case .Ended, .Cancelled, .Failed:
                delegate?.matrixViewDidEndBatchSelection(self)
                sender.selectionState = nil
            }
        }
    }