Zooms out a MKMapView to enclose all annotations (inc. current location).Swift.

zoomMapToFitAnnotations()

func zoomMapToFitAnnotations() {
        var zoomRect : MKMapRect = MKMapRectNull
        for annotation in mapView.annotations as! [MKAnnotation] {
            var annotationPoint = MKMapPointForCoordinate(annotation.coordinate)
            var pointRect =  MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 0)
            if  MKMapRectIsNull(zoomRect) {
                zoomRect = pointRect
            } else {
                zoomRect = MKMapRectUnion(zoomRect, pointRect)
            }
        }
        mapView.setVisibleMapRect(zoomRect, edgePadding:UIEdgeInsetsMake(10, 10, 10, 10), animated: false)
    }

Thanks perfectly !