swiftui - ERROR : " Trailing closure passed to parameter of type 'Binding<MapFeature?>' t

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import SwiftUI
import MapKit
import CoreLocation

struct ContentView: View {
    @State private var position: MapCameraPosition = .userLocation(fallback: .automatic)
    @State private var hazards: [(Double, Double)] = [] // Array of tuples for hazards

    @StateObject private var locationManager = LocationManager() // Reference to your LocationManager

    var body: some View {
        ZStack {
            // Map with annotations
error here >Map(position: $position) {  
                UserAnnotation()

                // Iterate over hazards to mark them
                for hazard in hazards {
                    MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: hazard.0, longitude: hazard.1)) {
                        VStack {
                            Image(systemName: "exclamationmark.triangle.fill")
                                .foregroundColor(.red)
                                .font(.title)
                            Text("Hazard")
                                .font(.caption)
                                .padding(4)
                                .background(Color.white.opacity(0.8))
                                .cornerRadius(5)
                        }
                    }
                }
            }
        }
    }
}

I am trying to iterate through an array that contains the coordinates of the user location when the button is pressed. Right now I only need to process each set of coordinates and mark a spot on the map at those coordinates. I am accurately getting the coordinates but the line,

Map(position: $position) {  

gives an error:

Trailing closure passed to parameter of type 'Binding<MapFeature?>' that does not accept a closure"

If I comment out:

for hazard in hazards {

Then it goes away and you get a bunch of errors that just conform to the line being commented out. The rest of the code has logic for a button that is pressed and adds coordinates to the hazards array of tuples. ie [(42.7963, -71.1545)] and other MapKit UI code that is irrelevant to the question.

I have tried changing the $position to an MKcoordinate that chatgpt suggested but it just created more problems and didn't help. This is my first time programming in swift so perhaps there is an easy fix but I cannot figure it out.

import SwiftUI
import MapKit
import CoreLocation

struct ContentView: View {
    @State private var position: MapCameraPosition = .userLocation(fallback: .automatic)
    @State private var hazards: [(Double, Double)] = [] // Array of tuples for hazards

    @StateObject private var locationManager = LocationManager() // Reference to your LocationManager

    var body: some View {
        ZStack {
            // Map with annotations
error here >Map(position: $position) {  
                UserAnnotation()

                // Iterate over hazards to mark them
                for hazard in hazards {
                    MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: hazard.0, longitude: hazard.1)) {
                        VStack {
                            Image(systemName: "exclamationmark.triangle.fill")
                                .foregroundColor(.red)
                                .font(.title)
                            Text("Hazard")
                                .font(.caption)
                                .padding(4)
                                .background(Color.white.opacity(0.8))
                                .cornerRadius(5)
                        }
                    }
                }
            }
        }
    }
}

I am trying to iterate through an array that contains the coordinates of the user location when the button is pressed. Right now I only need to process each set of coordinates and mark a spot on the map at those coordinates. I am accurately getting the coordinates but the line,

Map(position: $position) {  

gives an error:

Trailing closure passed to parameter of type 'Binding<MapFeature?>' that does not accept a closure"

If I comment out:

for hazard in hazards {

Then it goes away and you get a bunch of errors that just conform to the line being commented out. The rest of the code has logic for a button that is pressed and adds coordinates to the hazards array of tuples. ie [(42.7963, -71.1545)] and other MapKit UI code that is irrelevant to the question.

I have tried changing the $position to an MKcoordinate that chatgpt suggested but it just created more problems and didn't help. This is my first time programming in swift so perhaps there is an easy fix but I cannot figure it out.

• swiftui
• compiler-errors
• for-in-loop

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1 Answer 1

Sorted by: Reset to default 0

Inside Map you need to have Views, not procedural code. So try using this approach using a dedicated struct Hazard instead of an array of tuples, and importantly a ForEach loop instead of your procedural for hazard in hazards loop, to display the hazards on the Map.

Note MapAnnotation is deprecated use Annotation instead.

Example code:

struct Hazard: Identifiable {
    let id: UUID = UUID()
    let latitude: Double
    let longitude: Double
}

struct ContentView: View {
    @State private var position: MapCameraPosition = .userLocation(fallback: .automatic)
    
    @State private var hazards: [Hazard] = [
        Hazard(latitude: 35.69, longitude: 139.76),
        Hazard(latitude: 35.70, longitude: 139.77)
    ] // Array of hazards for testing
    
    //   @StateObject private var locationManager = LocationManager() // Reference to your LocationManager
    
    var body: some View {
        Map(position: $position) {
            UserAnnotation()
            
            // Iterate over hazards to mark them
            ForEach(hazards) { hazard in
                Annotation("", coordinate: CLLocationCoordinate2D(latitude: hazard.latitude, longitude: hazard.longitude)) {
                    VStack {
                        Image(systemName: "exclamationmark.triangle.fill")
                            .foregroundColor(.red)
                            .font(.title)
                        Text("Hazard")
                            .font(.caption)
                            .padding(4)
                            .background(Color.white.opacity(0.8))
                            .cornerRadius(5)
                    }
                }
            }
        }
    }
}

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