swift - 什么都不打印而不是 nil

Question

我创建了一个 View ，该 View 在 map 上显示用户位置，并在 View 中的两个标签中显示用户位置。它并不总是有 subThoroughfare，因此标签中印有“nil”。我该怎么做才能只打印任何内容而不是标签中的“nil”？感谢您的帮助

import UIKit
import CoreLocation
import MapKit

class Kart: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {

@IBOutlet var myMap: MKMapView!

var locationManager = CLLocationManager()



@IBOutlet var adress: UILabel!
@IBOutlet var adress2: UILabel!


override func viewDidLoad() {
    super.viewDidLoad()


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




    // Do any additional setup after loading the view.
}

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

func locationManager(manager: CLLocationManager!, didFailWithError error: NSError!) {
    println("Feil")
}

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {

    var userLocation:CLLocation = locations[0] as! CLLocation
    locationManager.stopUpdatingLocation()
    let location = CLLocationCoordinate2D(latitude: userLocation.coordinate.latitude, longitude: userLocation.coordinate.longitude)
    let span = MKCoordinateSpanMake(0.01, 0.01)
    let region = MKCoordinateRegion(center: location, span: span)
    myMap.setRegion(region, animated: true)



    CLGeocoder().reverseGeocodeLocation(userLocation, completionHandler: { (placemarks, error) -> Void in
        if (error != nil) {
            println(error)

        } else {
            if let p = CLPlacemark(placemark: placemarks?[0] as! CLPlacemark) {

                var subThoroughfare:String = ""

                if (p.subThoroughfare != nil) {
                    subThoroughfare = p.subThoroughfare

                }

                self.adress.text = "\(p.thoroughfare) \(p.subThoroughfare)"
                self.adress2.text = " \(p.postalCode) \(p.subLocality)"

            }

        }
    })
}

Answer 1

self.adress.text = "\(p.thoroughfare) \(p.subThoroughfare)" 

使用 p.subThoroughfare 而不是 subThoroughfare。此外，您可以为此使用 nil 合并运算符 (??)

var subThoroughfare = p.subThoroughfare ?? "" 

如果 p.subThoroughfare 不为 nil，将计算为 p.subThoroughfare，否则将计算为 ""

所以:

var subThoroughfare = p.subThoroughfare ?? "" 
self.adress.text = "\(p.thoroughfare) \(subThoroughfare)"
self.adress2.text = " \(p.postalCode) \(p.subLocality)"