CompletionHandler未执行

Question

我试图获得＆＃34; locality＆＃34;来自使用CLGeocoder.reverseGeocodeLocation的坐标，但当执行到达completionHandler时，括号内的代码将完全跳过self.currentPlace = (self.place?.locality)! + ", " + (self.place?.thoroughfare)!冻结应用程序。

我哪里错了？

func updateLocation() {
    let location = CLLocation.init(latitude: currentCoordinates.latitude, longitude: currentCoordinates.longitude)
    let geocoder = CLGeocoder()
    geocoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error)  in
        if (error != nil) {
            print("Error")
        }else {
        let pm = placemarks as [CLPlacemark]!
        if pm.count > 0 {
        self.place = pm.first
        self.stopUpdatingLocation()
           }
        }
    })
    self.currentPlace = (self.place?.locality)! + ", " + (self.place?.thoroughfare)!
}

Answer 1

这称为异步编程。反向地理编码完成后，会在一段时间后调用完成处理程序。您需要在处理程序内调用UI更新。

您可以显示某种加载程序，它向用户指示正在进行操作。

func updateLocation() {
    let location = CLLocation.init(latitude: currentCoordinates.latitude, longitude: currentCoordinates.longitude)
    let geocoder = CLGeocoder()

    //Show loader here
    geocoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error)  in
        //hide loader here
        if (error != nil) {
            print("Error")
        }else {
        let pm = placemarks as [CLPlacemark]!
        if pm.count > 0 {
        self.place = pm.first
        self.currentPlace = (self.place?.locality)! + ", " + (self.place?.thoroughfare)!
        self.stopUpdatingLocation()
           }
        }
    })
}