如何在Swift 3中的mapview上生成不同的图钉？

class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet weak var mapView: MKMapView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        mapView.delegate = self
        
        // 添加一些示例数据
        let locations = [
            ["title": "地点1", "latitude": 37.331686, "longitude": -122.030656],
            ["title": "地点2", "latitude": 37.332686, "longitude": -122.031656],
            ["title": "地点3", "latitude": 37.333686, "longitude": -122.032656]
        ]
        
        // 遍历数据，创建并添加图钉
        for location in locations {
            if let title = location["title"], let latitude = location["latitude"] as? CLLocationDegrees, let longitude = location["longitude"] as? CLLocationDegrees {
                let annotation = MKPointAnnotation()
                annotation.title = title
                annotation.coordinate = CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
                mapView.addAnnotation(annotation)
            }
        }
    }
    
    // 自定义图钉样式
    func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        if annotation is MKUserLocation {
            return nil
        }
        
        let identifier = "CustomPinAnnotationView"
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: identifier) as? MKPinAnnotationView
        
        if annotationView == nil {
            annotationView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
            annotationView?.canShowCallout = true
        } else {
            annotationView?.annotation = annotation
        }
        
        // 设置不同的图钉颜色
        if annotation.title == "地点1" {
            annotationView?.pinTintColor = .red
        } else if annotation.title == "地点2" {
            annotationView?.pinTintColor = .green
        } else if annotation.title == "地点3" {
            annotationView?.pinTintColor = .blue
        }
        
        return annotationView
    }
}