如何删除地图中的特定标记

Question

我在地图（位于我的 ContentView 上）中设置了 3 个标记（0、1、2）。现在我只想删除标记 0（不是 1 也不是 2）。

我发现的只是“removeAnnotation”，尽管我的标记只是一个标记，没有声明为注释。尽管如此，我从堆栈溢出中得到了答案（https://stackoverflow.com/questions/47959193/swift-4-to-remove-only-one-annotation-not-all/47965214，但它不起作用.

我是 Swift 的初学者，所以问题似乎（除了 removeAnnotation-Question 之外）出在我的代码本身中。

我的代码：

import SwiftUI
import MapKit

struct MyLocationsArray: Identifiable {
    let id = UUID()                          
    let number: Int                         
    let name: String                        
    let label: String  
    let coordinates: CLLocationCoordinate2D
    
}


struct ContentView: View {
    
    @State var myLocs = [
        MyLocationsArray(number: 0, name: "name A", label: "label A", coordinates: CLLocationCoordinate2D(latitude: 39.873563, longitude: 3.170857999999953)),
        
        MyLocationsArray(number: 1, name: "name B", label: "label B", coordinates: CLLocationCoordinate2D(latitude: 39.654235, longitude: 2.947624)),
        
        MyLocationsArray(number: 2, name: "name C", label: "label C", coordinates: CLLocationCoordinate2D(latitude: 39.530, longitude: 2.90))
    ]

 
    
    var body: some View {
        Map()
        {
             Marker(myLocs[0].name, coordinate: myLocs[0].coordinates)
             Marker(myLocs[1].name, coordinate: myLocs[1].coordinates)
             Marker(myLocs[2].name, coordinate: myLocs[2].coordinates)
        }
        
        Button("Button title") {
            removeSpecificAnnotation()
        }
        
        
    }
    
    func removeSpecificAnnotation() {
        for n in myLocs {
            
            if let name = n.name, name == "name A" { // "Conditioner for conditional binding must have Optional type, not 'String'": But my "name" ist a String. 
                removeAnnotation(n)   // "Cannot find removeAnnotation in Scope": But with whatelse  can I remove a Marker?
            }
        }
    }
}

我在 stackoverflow 中搜索并找到了答案，但不知何故它不适用于我的代码。在互联网上，除了将图钉颜色更改为透明之外，我没有找到“如何删除标记”的答案。答，正如我所说，这也可能是我的通用代码，因为我是初学者。

Answer 1

在 SwiftUI 中，您可以使用

data

来实现您想要的。

因此请尝试使用

data

( myLocs) 选择然后删除所选的方法

MyLocation

，如示例代码所示。

struct MyLocation: Identifiable, Hashable {
    let id = UUID()
    var number: Int
    var name: String
    var label: String
    var latitude: Double
    var longitude: Double
    
    var coordinates: CLLocationCoordinate2D {
      CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
    }
    
    init(number: Int, name: String, label: String, coordinates: CLLocationCoordinate2D) {
        self.number = number
        self.name = name
        self.label = label
        self.latitude = coordinates.latitude
        self.longitude = coordinates.longitude
    }
}

struct ContentView: View {
    
    @State private var myLocs = [
        MyLocation(number: 0, name: "name A", label: "label A", coordinates: CLLocationCoordinate2D(latitude: 39.873563, longitude: 3.170857999999953)),
        
        MyLocation(number: 1, name: "name B", label: "label B", coordinates: CLLocationCoordinate2D(latitude: 39.654235, longitude: 2.947624)),
        
        MyLocation(number: 2, name: "name C", label: "label C", coordinates: CLLocationCoordinate2D(latitude: 39.530, longitude: 2.90))
    ]
    
    @State private var selection: MyLocation?
    
    var body: some View {
        Map(selection: $selection) {
            ForEach(myLocs) { loc in
                Marker(loc.name, coordinate: loc.coordinates).tag(loc)
            }
        }
        Button("Remove selected") {
            removeSelectedMarker()
        }
    }
    
    func removeSelectedMarker() {
        if let index = myLocs.firstIndex(where: {$0.id == selection?.id}){
            myLocs.remove(at: index)
        }
    }
}