swift 闭包中的变量范围 wrt CLGeocoder()

Question

谁能帮我理解为什么下面的代码会有这样的输出：

[<+37.49638550,-122.31160280> +/- 5.00m (speed 32.65 mps / course 294.26) @ 7/27/16, 4:34:19 AM Eastern Daylight Time]

n/a Belmont Belmont

Belmont 1

也就是说，为什么变量 locality 在特定点打印时的值为 "n/a" 而 localityVC & localityGlobal 从不做？这纯粹是范围问题还是与 CLGeocoder() 有关？谢谢

import UIKit
import MapKit
import CoreLocation

var localityGlobal: String = "n/a"

class ViewController: UIViewController, CLLocationManagerDelegate {

    let locationManager = CLLocationManager()
    var localityVC: String = "n/a"

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        print("hello")

        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        print(locations)

        let userLocation: CLLocation = locations[0]
        var locality: String = "n/a"

        CLGeocoder().reverseGeocodeLocation(userLocation, completionHandler: {(placemarks, error) -> Void in
            if error != nil {
                print("CLGeocoder.reverseGeocodeLocation() failed")
                return
            }
            if placemarks!.count > 0 {
                locality = placemarks![0].locality!
                self.localityVC = placemarks![0].locality!
                localityGlobal = placemarks![0].locality!
                print(locality, placemarks!.count)

            } else {
                print("CLGeocoder.reverseGeocodeLocation() error in geocoder data")
            }
        })

        print(locality, localityVC, localityGlobal)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

为了使上述运行您还需要：

Build Phases -> Link Binary with Libraries包括 CoreLocation.framework,
Info.plist必须有变量 NSLocationWhenInUseUsageDescription 和 NSLocationAlwaysUsageDescription集，
Simulator -> Debug -> Location 设置为 Apple、City Bicycle Ride、City Run 或 Freeway Drive

我运行宁 xcode 7.3.1 (7D1014)

Answer 1

这不是范围问题，而是时间问题。您得到 n/a 是因为在执行该打印语句时闭包尚未运行。

其他变量保留了先前调用的值。

swift 闭包中的变量范围 wrt CLGeocoder()

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