ios - 从另一个函数 : mapView = nil 访问我的 mapView var

Question

我试图通过函数在 mapView 上放置一些注释，但 mapView 在调试器中显示为 nil。我从不同的类调用下面的函数，调用似乎通过设置一些断点来工作。它只是在尝试将注释数组添加到 mapView 时出错。

let temp = MapViewController()
temp.createCurrentSevereAnnotations()

这是我的 MapViewController 代码:

import UIKit
import MapKit

final class MapViewController : UIViewController, MKMapViewDelegate{

@IBOutlet weak var mapView: MKMapView!

    // Change the Map Type from the tool bar segmented button.
//this function works fine.  mapView is not nil.
@IBAction func changeMapType(sender: UISegmentedControl) {
    switch (sender.selectedSegmentIndex) {
    case 0:
        mapView.mapType = .Standard
    case 1:
        mapView.mapType = .Hybrid
    default:
        mapView.mapType = .Satellite

    } //^ this func works fine
 }
    //Puts an array of CustomPointAnnotation on the map.
 func createCurrentSevereAnnotations() {
    var annotations: Array = [CustomPointAnnotation]()
    let severeReports = currentSevereReports

    for item in severeReports
    {
        let annotation = CustomPointAnnotation(latitude: Double(item.lat!), longitude: Double(item.lon!))
        print("The lat is: \(item.lat!)")
        print("The lon is: \(item.lon!)")
        switch(Int(item.type!))
        {
        case 1:
            annotation.imageName = "ef0"
            annotation.type = "Tornado"
            break
        case 2:
            annotation.imageName = "wind"
            annotation.type = "Wind"
            break
        default:
            annotation.imageName = "hail"
            annotation.type = "Hail"
            break
        }
        print("item type : \(annotation.type)")
        annotation.title = item.magnitude
        annotation.subtitle = item.location
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateStyle = .MediumStyle
        annotation.time = item.time
        annotation.county = item.county
        annotation.remarks = item.remarks

        annotations.append(annotation)
    }
    print("Annotations count = \(annotations.count)") //<- works
    mapView.addAnnotations(annotations) //<- this is where mapView is nil
 }


    // The class for our CustomPointAnnotation
 class CustomPointAnnotation: NSObject, MKAnnotation {
    var title: String? //mag
    var subtitle: String? //location
    var latitude: Double
    var longitude:Double
    var imageName: String!
    var time: String?
    var remarks : String?
    var county: String?
    var type: String?
    var comments: String?


    var coordinate: CLLocationCoordinate2D {
        return CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
    }

    init(latitude: Double, longitude: Double) {
        self.latitude = latitude
        self.longitude = longitude
    }
 }
}

Answer 1

问题就在这里

let temp = MapViewController()

这不是实例化 View Controller 的方式。

---

您应该使用从 Storyboard 中加载。 (click here to check apple documentation)

func instantiateViewControllerWithIdentifier(_ identifier: String) -> UIViewController

---

尝试用这种方式实例化temp。

let temp = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("MapViewControllerIdentifier") as UIViewController
self.presentViewController(temp, animated: true, completion: nil)

您应该为您的 View Controller 定义一个标识符(我在示例中使用“MapViewControllerIdentifier”) ，您可以在应用的 storyboard 的 View 中执行此操作。