Question

我正在阅读一本名为“iOS编程第5版”的书，由大书呆子分支。

此代码在地图视图中生成分段视图，每次在运行时更改分段时，它都会崩溃：

线程1：信号SIGABRT

当我使用最新版本时，可能与书中的旧版Swift有关。

这是我的代码：

class MapViewController: UIViewController
{
var mapView: MKMapView!

override func loadView()
{
    //Create a map view
    mapView = MKMapView ()

    //Set it as *the* view of this view controller
    view = mapView

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

    segmentedControl.addTarget(self, action: Selector(("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()
{
    // Always call the super implementation of ViewDidLoad
    super.viewDidLoad()
    print ("MapViewController loaded its view")
}



}

我该如何解决这个问题？

Answer 1

尝试在操作方法中添加@objc属性（同样，根据Swift 3，也可以使用_删除参数标签）：

@objc func mapTypeChanged(_ segControl: UISegmentedControl) {
    ...
}

作为简化（和代码大小优化），Swift 4 now further restricts哪些方法会自动向Objective-C公开 - 即使是NSObject子类，例如上面的MapViewController类。

顺便说一句，使用@IBAction属性也会将您的方法暴露给Objective-C。

IOS：切换段时的'线程1：信号SIGABRT'

1 个答案: