「こする」を表現するカスタムUIGestureRecognizer

必要になったので作ってみました。
必ずしも左右にこすらなくても反応してしまうのはご愛嬌で。
あと最初ハマったのでこちらも参照ください。
http://qiita.com/okitsutakatomo/items/37e717f2b34a957cca8f

//
//  UINaderuGestureRecognizer.swift
//
//  Created by Takatomo Okitsu on 2014/12/25.
//  Copyright (c) 2014年 Takatomo Okitsu. All rights reserved.
//

import UIKit

var kNaderuGestureReturnCount = 2
var kNaderuGestureReturnDistance:CGFloat = 20

class UINaderuGestureRecognizer :UIGestureRecognizer {

    var timeOutTimer:NSTimer?
    var startingPoint:CGPoint?
    var returnCount:Int = 0

    override func reset() {
        startingPoint = nil
        returnCount = 0
    }

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
        self.invalidateTimer()

        if touches.count > 1 {
            self.state = UIGestureRecognizerState.Failed
        } else {
            let touch:UITouch = touches.anyObject()? as UITouch
            if touch.tapCount > 1 {
                self.state = .Failed
            } else {
                return
            }
        }
    }

    override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {
        let touch:UITouch = touches.anyObject()? as UITouch
        if self.state == .Possible {
            if startingPoint == nil {
                startingPoint = touch.locationInView(nil)
                timeOutTimer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "handleTimeOut", userInfo: nil, repeats: false)
            } else {
                let point = touch.locationInView(nil)
                let distance = (point - startingPoint!).length
                if distance > kNaderuGestureReturnDistance {
                    returnCount++
                    if returnCount >= kNaderuGestureReturnCount {
                        self.state = UIGestureRecognizerState.Ended //event fired
                    } else {
                        startingPoint = point
                    }
                }
            }
        } else {
            self.state = .Failed
        }
    }

    override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {
        self.invalidateTimer()
        self.state = .Failed
    }

    override func touchesCancelled(touches: NSSet, withEvent event: UIEvent) {
        self.invalidateTimer()
        self.state = .Cancelled
    }

    func invalidateTimer() {
        timeOutTimer?.invalidate()
        timeOutTimer = nil;
    }

    func handleTimeOut() {
        self.invalidateTimer()
        self.state = .Failed
    }
}