swift - 调用中参数 'completionHandler' 缺少参数

Question

我使用了 geocodeAddressString 函数，它在 swift 1.0 中有效，但在 swift2 中无效。谁能告诉我我的代码有什么问题以及如何解决这个问题？谢谢!

geocoder.geocodeAddressString(address, {(placemarks: [AnyObject], error: NSError) -> Void in  //Error: Missing argument for parameter 'completionHandler' in call

        if let placemark = placemarks?[0] as? CLPlacemark {
            let annotation = MKPointAnnotation()
            let location:CLLocationCoordinate2D = CLLocationCoordinate2DMake(placemark.location.coordinate.latitude, placemark.location.coordinate.longitude)
            annotation.coordinate = location
            annotation.title = "\(StudentArray[student].firstName), \(StudentArray[student].lastName)"
            annotation.subtitle = "\(StudentArray[student].grade)"
            self.mapView.addAnnotation(annotation)
        }

    })

Answer 1

要么指定completionHandler参数名:

geocoder.geocodeAddressString(address, completionHandler: { placemarks, error in
    if let placemark = placemarks.first as? CLPlacemark {
        let annotation = MKPointAnnotation()
        let location = CLLocationCoordinate2DMake(placemark.location.coordinate.latitude, placemark.location.coordinate.longitude)
        annotation.coordinate = location
        annotation.title = "\(StudentArray[student].firstName), \(StudentArray[student].lastName)"
        annotation.subtitle = "\(StudentArray[student].grade)"
        self.mapView.addAnnotation(annotation)
    }
})

或者使用尾随闭包语法(参见 The Swift Programming Language 的 Closures 章的 Trailing Closure 部分)，您可以在其中将闭包从 ( 和 ) 并将其放在 ) 之后:

geocoder.geocodeAddressString(address) { placemarks, error in
    if let placemark = placemarks.first as? CLPlacemark {
        let annotation = MKPointAnnotation()
        let location = CLLocationCoordinate2DMake(placemark.location.coordinate.latitude, placemark.location.coordinate.longitude)
        annotation.coordinate = location
        annotation.title = "\(StudentArray[student].firstName), \(StudentArray[student].lastName)"
        annotation.subtitle = "\(StudentArray[student].grade)"
        self.mapView.addAnnotation(annotation)
    }
}