Swift为什么不更新闭包之外的变量？ [英] Why does Swift not update the variables outside the closure?

问题描述

这是我使用的代码-问题是返回的CLLocationCoordinate2D对象中的纬度和经度值均为-1，即它们的初始化值。我缺少什么？

Here's the code I'm using -- Problem is that the value of latitude and longitude in the returned CLLocationCoordinate2D object are both -1, their initialized values. What am I missing?

func getLocationInfoForAddress(shop: store) -> CLLocationCoordinate2D {

    var address = getAddressInOneLine(shop)
    var latitude: CLLocationDegrees = -1
    var longitude: CLLocationDegrees = -1

    var geocoder = CLGeocoder()
    geocoder.geocodeAddressString(address, {(placemarks: [AnyObject]!, error: NSError!) -> Void in
        if let placemark = placemarks?[0] as? CLPlacemark {
            latitude = placemark.location.coordinate.latitude
            longitude = placemark.location.coordinate.longitude
        }
    })

    var location: CLLocationCoordinate2D = CLLocationCoordinate2D(latitude: latitude,longitude: longitude)
    return location
}

推荐答案

作为@NateCook答案的补充，一种重构代码的可能方法是：

As a complement to @NateCook's answer, one possible way to refactor your code is:

func getLocationInfoForAddress(shop: store) {
    var address = getAddressInOneLine(shop)

    var geocoder = CLGeocoder()
    geocoder.geocodeAddressString(address, {(placemarks: [AnyObject]!, error: NSError!) -> Void in
        if let placemark = placemarks?[0] as? CLPlacemark {
            var latitude = placemark.location.coordinate.latitude
            var longitude = placemark.location.coordinate.longitude

            var location: CLLocationCoordinate2D = CLLocationCoordinate2D(latitude: latitude,longitude: longitude)
            self.didReceiveGeocodeAddress(location)
        }
    })
}

func didReceiveGeocodeAddress(location: CLLocationCoordinate2D) {
    // do something
}

获取位置后，您将调用相同的方法类传递位置。由于处理程序关闭是在主线程中执行的，因此可以安全地更新UI组件。

When the location is obtained, you invoke a method of the same class passing the location. Since the handler closure is executed in the main thread, you can safely update UI components.

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