類型 '的MapViewController' 沒有成員 'mapTypeChanged' 夫特大書呆子農場指南

Question

[類型 '的MapViewController' 沒有成員 'mapTypeChanged'] [2] 管線：

action: #selector(MapViewController.mapTypeChanged(_:)), 

有一種方法mapTypeChanged在代碼的底部，所以我不確定爲什麼錯誤說沒有成員mapTypeChanged？我猜mapTypeChanged需要聲明的變量（全球？）

import UIKit 
import MapKit 


class MapViewController: UIViewController { 

    var mapView: MKMapView! 

    override func loadView() { 

     mapView = MKMapView() 
     view = mapView 

     let segmentedControl 
      = UISegmentedControl(items: ["Standard", "Hybrid", "Satellite"]) 
     segmentedControl.backgroundColor 
      = UIColor.white.withAlphaComponent(0.5) 
     segmentedControl.selectedSegmentIndex = 0 

     segmentedControl.addTarget(self, 
            action: #selector(MapViewController.mapTypeChanged(_:)), 
            for: .valueChanged) 
segmentedControl.translatesAutoresizingMaskIntoConstraints = false 
     view.addSubview(segmentedControl) 

     let topConstraint 
      = segmentedControl.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor, constant: 8) 
     let margins = view.layoutMarginsGuide 
     let leadingConstraint = 
      segmentedControl.leadingAnchor.constraint(equalTo: margins.leadingAnchor) 
     let trailingConstraint = 
      segmentedControl.trailingAnchor.constraint(equalTo: margins.trailingAnchor) 

     topConstraint.isActive = true 
     leadingConstraint.isActive = true 
     trailingConstraint.isActive = true 

     func mapTypeChanged(_segControl: UISegmentedControl) { 
      switch _segControl.selectedSegmentIndex { 
      case 0: 
       mapView.mapType = .standard 
      case 1: 
       mapView.mapType = .hybrid 
      case 2: 
       mapView.mapType = .satellite 
      default: 
       break 
      } 
     } 
    } 


    override func viewDidLoad() { 
     super.viewDidLoad() 

     print("MapViewController Loaded its view.") 

    } 

} 

Answer 1

#selector(MapViewController.mapTypeChanged(_:)) 

意味着 「調用mapTypeChanged方法」。因此您需要執行mapTypeChanged。

func mapTypeChanged(_ sender: UISegmentedControl) { 
    print(sender.selectedSegmentIndex) 
}