Wie lösche ich die pins auf einer mapview in swift?

Teil meiner app enthält eine mapview, die sucht automatisch auf der Basis eines Schlüsselworts. Ich habe eine textbox und eine Schaltfläche "suchen" meiner mapview, aber mir ist aufgefallen das die pins nicht klar aus der vorherigen Suche. Wie lösche ich die Karte von allen pins, bevor Sie die neue Suche?

import UIKit
import MapKit
import CoreLocation
import iAd

class MapClass: UIViewController, CLLocationManagerDelegate, UISearchBarDelegate, ADBannerViewDelegate {

var searchController:UISearchController!
var annotation:MKAnnotation!
var localSearchRequest:MKLocalSearchRequest!
var localSearch:MKLocalSearch!
var localSearchResponse:MKLocalSearchResponse!
var error:NSError!
var pointAnnotation:MKPointAnnotation!
var pinAnnotationView:MKPinAnnotationView!

var holidayKeyWord = NSString()

@IBOutlet var mapSearchTextbox: UITextField!
@IBOutlet weak var mapView: MKMapView!
@IBOutlet var adBannerView: ADBannerView!
var locationManager: CLLocationManager!

let searchRadius: CLLocationDistance = 2000

override func viewDidLoad() {
    super.viewDidLoad()

    holidayKeyWord = "Restaurant"

    println(holidayKeyWord)
    mapSearchTextbox.text = holidayKeyWord as String

    self.canDisplayBannerAds = true
    self.adBannerView?.delegate = self
    self.adBannerView?.hidden = false

    if (CLLocationManager.locationServicesEnabled())
    {
        locationManager = CLLocationManager()
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()
    }

}


@IBAction func mapSearchButton(sender: UIButton) {

    //clear pins

    var holidayKeyWord = mapSearchTextbox.text


    if (CLLocationManager.locationServicesEnabled())
    {
        let request = MKLocalSearchRequest()
        request.naturalLanguageQuery = holidayKeyWord as String
        let search = MKLocalSearch(request: request)
        search.startWithCompletionHandler {
            (response: MKLocalSearchResponse!, error: NSError!) in

            for item in response.mapItems as! [MKMapItem] {
                println(item.name)
                self.addPinToMapView(item.name, latitude: item.placemark.location.coordinate.latitude, longitude: item.placemark.location.coordinate.longitude)

            }
        }
    }



}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    //replace spaces with dashes in wikiDate string

    if (segue.identifier == "amazonToWeb") {
        var wikiDate = "http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Ddigital-text&field-keywords=\(holidayKeyWord)"
        var DestViewController : WebBrowser = segue.destinationViewController as! WebBrowser
        DestViewController.wikiDate = wikiDate
    }

    if (segue.identifier == "searchToWeb") {
        var wikiDate = "http://www.bing.com"
        var DestViewController : WebBrowser = segue.destinationViewController as! WebBrowser
        DestViewController.wikiDate = wikiDate
    }

    if (segue.identifier == "ebayToWeb") {
        var wikiDate = "http://search.ebay.com/\(holidayKeyWord)"
        var DestViewController : WebBrowser = segue.destinationViewController as! WebBrowser
        DestViewController.wikiDate = wikiDate
    }

}

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {

    let location = locations.last as! CLLocation
    let center = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
    let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
    self.mapView.setRegion(region, animated: true)
    var latitude: Double = location.coordinate.latitude
    var longitude: Double = location.coordinate.longitude
    let initialLocation = CLLocation(latitude: latitude, longitude: longitude)
    //1
    let request = MKLocalSearchRequest()
    request.naturalLanguageQuery = holidayKeyWord as String
    //2
    let span = MKCoordinateSpan(latitudeDelta: 0.1, longitudeDelta: 0.1)

    request.region = MKCoordinateRegion(center: initialLocation.coordinate, span: span)
    //3
    let search = MKLocalSearch(request: request)
    search.startWithCompletionHandler {
        (response: MKLocalSearchResponse!, error: NSError!) in


        for item in response.mapItems as! [MKMapItem] {
            println(item.name)
            //println("Latitude = \(item.placemark.location.coordinate.latitude)")
            //println("Longitude = \(item.placemark.location.coordinate.longitude)")
            self.addPinToMapView(item.name, latitude: item.placemark.location.coordinate.latitude, longitude: item.placemark.location.coordinate.longitude)
        }
    }

    locationManager.stopUpdatingLocation()

    let coordinateRegion = MKCoordinateRegionMakeWithDistance(initialLocation.coordinate, searchRadius * 2.0, searchRadius * 2.0)
    mapView.setRegion(coordinateRegion, animated: true)

}


func addPinToMapView(title: String, latitude: CLLocationDegrees, longitude: CLLocationDegrees) {
    let location = CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
    let annotation = MyAnnotation(coordinate: location, title: title)

    mapView.addAnnotation(annotation)

}

func removePinFromMapView(title: String, latitude: CLLocationDegrees, longitude: CLLocationDegrees) {
    let location = CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
    let annotation = MyAnnotation(coordinate: location, title: title)

    mapView.removeAnnotation(annotation)

}


func locationManager(manager: CLLocationManager!, didFailWithError error: NSError!)
{
    println("Error: " + error.localizedDescription)
}