在地圖視圖上使用軌道位置時出現可變錯誤

Question

我試圖在地圖視圖上顯示和跟蹤位置。我得到的錯誤：

Use of local Variable 'locationManager' before declaration

的錯誤是對的LocationManager的所有行：

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

我已經ViewDidLoad之前聲明var locationManager = CLLocationManager()。

我有我的變數在錯誤的地方嗎？

import UIKit 
import MapKit 
import CoreLocation 

class InfoViewController: UIViewController,UIGestureRecognizerDelegate, CLLocationManagerDelegate { 


    // Outlets 
    @IBOutlet weak var infoImageView: UIImageView! 


    @IBOutlet weak var nameLabel: UILabel! 


    @IBOutlet weak var categoryLabel: UILabel! 


    @IBAction func urlButton(sender: UIButton) { 
    } 

    @IBOutlet weak var mapView: MKMapView! 

    // Variables 

    var gesture: UISwipeGestureRecognizer! 

    var store: Store! 

    var locationManager = CLLocationManager() 




    override func viewDidLoad() { 
     super.viewDidLoad() 

     // Do any additional setup after loading the view. 

     // Background image 
     self.infoImageView.image = UIImage(data: store.photo) 

     // Set label text 
     self.nameLabel.text = store.name 

     // Set category text 
     var categoryText = String() 
     for category in store.storeCategories { 
      if !categoryText.isEmpty { 
       categoryText += ", " 
      } 
      categoryText += category.name 
     } 

     categoryLabel.text = categoryText 




     if (CLLocationManager.locationServicesEnabled()) 
     { 

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

     } 

     func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) { 
      let location = locations.last as! CLLocation 

      let center = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude) 
      let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)) 

      self.mapView.setRegion(region, animated: true) 
      } 

     // Gesture recoginizer 
     gesture = UISwipeGestureRecognizer(target: self, action: "dismissView") 
     self.gesture.direction = UISwipeGestureRecognizerDirection.Up 

     self.view.addGestureRecognizer(self.gesture) 

    } 

    func dismissView() { 
     self.dismissViewControllerAnimated(true, completion: nil) 
    } 


} 

Answer 1

您必須聲明的LocationManager塊之外，在這種情況下，你已經嘗試聲明它的if-block這將給使它成爲一個局部變量中。聲明if-block.工作示例代碼以外的變量爲作業：

var locationManager = CLLocationManager() 

override func viewDidLoad() { 

正如你所看到的，我已經宣佈在同一水平viewDidLoad()方法的變量，給它一個更更大的範圍。

，然後在你的，如果塊，你可以這樣做：

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

請注意，我刪除了locationManager = CLLocationManager()第一線，因爲它已經被實例化。

此外，locationManager的函數不能位於viewDidLoad方法內。

此外，我不明白爲什麼你的if-block是包裝的方法。

Answer 2

正如Hassan所說，您只需要將locationManager(...)函數聲明移出if塊。要認識到的重要一點是，在Swift中，可以像變量一樣傳遞函數的引用。因此，locationManager(...)函數的聲明（將被稱爲locationManager）將覆蓋變量的聲明。

現在您的代碼應該是這樣的：

import UIKit 
import MapKit 
import CoreLocation 

class InfoViewController: UIViewController,UIGestureRecognizerDelegate, CLLocationManagerDelegate { 


    // Outlets 
    @IBOutlet weak var infoImageView: UIImageView! 


    @IBOutlet weak var nameLabel: UILabel! 


    @IBOutlet weak var categoryLabel: UILabel! 


    @IBAction func urlButton(sender: UIButton) { 
    } 

    @IBOutlet weak var mapView: MKMapView! 

    // Variables 

    var gesture: UISwipeGestureRecognizer! 

    var store: Store! 

    var locationManager = CLLocationManager() 




    override func viewDidLoad() { 
     super.viewDidLoad() 

     // Do any additional setup after loading the view. 

     // Background image 
     self.infoImageView.image = UIImage(data: store.photo) 

     // Set label text 
     self.nameLabel.text = store.name 

     // Set category text 
     var categoryText = String() 
     for category in store.storeCategories { 
      if !categoryText.isEmpty { 
       categoryText += ", " 
      } 
      categoryText += category.name 
     } 

     categoryLabel.text = categoryText 

     if (CLLocationManager.locationServicesEnabled()) 
     { 

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

     // Gesture recoginizer 
     gesture = UISwipeGestureRecognizer(target: self, action: "dismissView") 
     self.gesture.direction = UISwipeGestureRecognizerDirection.Up 

     self.view.addGestureRecognizer(self.gesture) 

    } 

    func dismissView() { 
     self.dismissViewControllerAnimated(true, completion: nil) 
    } 

    func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) { 
     let location = locations.last as! CLLocation 

     let center = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude) 
     let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)) 

     self.mapView.setRegion(region, animated: true) 
    } 

} 

此外，當您設置此對象的委託，預計該方法是從類直接訪問。同樣，在Swift中，當涉及範圍時，方法就像變量一樣。所以當你在另一個方法中聲明時，它不能從類中訪問。當你在課堂上直接聲明時，可以調用delegate.locationManager(...)。