Ios XCode-在MKAnnotationView中将按钮设置为leftCalloutAccessoryView

我正在尝试将文本为“button”的按钮设置为左侧详图索引附件视图。这是我到目前为止所拥有的

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if let annotation = annotation as? LocationObjects{
        if let view = mapView.dequeueReusableAnnotationView(withIdentifier: annotation.identifier){
            return view
        }else{
            let view = MKAnnotationView(annotation: annotation, reuseIdentifier: annotation.identifier)
            view.isEnabled = true
            view.canShowCallout = true
            view.image = annotationPin

            let test = UIButton(type: .system)
            test.setTitle("Button", for: .normal)

            view.leftCalloutAccessoryView = test
            return view
        }
    }
    return nil
}

之后会抛出一个错误

test.setTitle("Button", for: .normal)

但如果我删除该行并设置

let test = UIButton(type: .system)

到

如何将按钮设置为文本而不是图像或默认系统图标

谢谢

let test = UIButton(type: .detailDisclosure)