如何在按钮 func 中传递特定 func 的常量值以将其用作导航的目的地

Posted 2023-03-11

【中文标题】如何在按钮 func 中传递特定 func 的常量值以将其用作导航的目的地

【英文标题】：How to pass the value of a constant of a specific func in a button func to use it as destination of the navigation

【发布时间】：2017-11-06 16:08:41

【问题描述】：

如何在这个函数中使用常量

func didSelect(place:QPlace) 

    guard let coordinates = place.location  else 
        return
    

    // clear current marker
    marker?.map = nil

    // add marker
    marker = GMSMarker()
    marker?.position = coordinates
    marker?.title = place.name
    marker?.map = mapView
    mapView.selectedMarker = marker
    moveToMarker(marker!)

    // update bottom info panel view
    let desc = place.getDescription()
    descriptionLabel.text = desc.characters.count > 0 ? desc : "-"
    distanceLabel.text = "-"

    // update distance
    if userLocation != nil 
        let dist = distance(from: userLocation!, to: coordinates)
        distanceLabel.text = String.init(format: "Distance %.2f meters", dist)
        self.drawPath(startLocation: userLocation!, endLocation: coordinates)
    

    title = place.name

（所以常量coordinates）在这里得到目的地

  @IBAction func navigationStart(_ sender: Any) 

  let coordinate = CLLocationCoordinate2DMake(51.5007, -0.1246)
    let placeMark = MKPlacemark(coordinate: coordinate)
    let mapItem = MKMapItem(placemark: placeMark)
    mapItem.name = "Big Ben"
    mapItem.openInMaps(launchOptions: [MKLaunchOptionsDirectionsModeKey: MKLaunchOptionsDirectionsModeDriving])

点击按钮后我在哪里打开地图，所以我想要让坐标 = 坐标，我该怎么做？

【问题讨论】：

将destPosition 声明为属性（在类级别）？

【参考方案1】：

基本上看起来您想要保存对传入位置的引用并在以后使用它。所以这表明：

创建实例变量var destination: CLLocationCoordinate2D?

从方法中分配目的地：

func didSelect(place:QPlace) 
    destination = place.location

设置目的地

@IBAction func navigationStart(_ sender: Any) 
    if let coordinate = self.destination 
        let placeMark = MKPlacemark(coordinate: coordinate)
        let mapItem = MKMapItem(placemark: placeMark)
        mapItem.name = "Big Ben"
        mapItem.openInMaps(launchOptions: 
            [MKLaunchOptionsDirectionsModeKey: 
            MKLaunchOptionsDirectionsModeDriving])
    

假设它有效，我将它基于您的代码。没有检查类型。如果它不起作用，那应该很容易解决。但主要的逻辑是这样的。

更新 2.:

func didSelect(place:QPlace) 
    guard let coordinates = place.location  else 
        return
    
    // ADD THIS
    self.destination = coordinates

    // clear current marker
    marker?.map = nil

    // add marker
    marker = GMSMarker()
    marker?.position = coordinates
    marker?.title = place.name
    marker?.map = mapView
    mapView.selectedMarker = marker
    moveToMarker(marker!)

    // update bottom info panel view
    let desc = place.getDescription()
    descriptionLabel.text = desc.characters.count > 0 ? desc : "-"
    distanceLabel.text = "-"

    // update distance
    if userLocation != nil 
        let dist = distance(from: userLocation!, to: coordinates)
        distanceLabel.text = String.init(format: "Distance %.2f meters", dist)
        self.drawPath(startLocation: userLocation!, endLocation: coordinates)
    

    title = place.name

【讨论】：

对不起，我用完整的功能编辑了问题，如果我拿掉保护让，我会在代码中得到很多错误

@Tvenden 试试这个。再次，逻辑是相同的。保持对位置的引用并在按钮单击方法中更新到该位置。