Plotting map annotations from a JSON response

Question

Created Oct ’20

Replies 2

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I'm trying to plot out map annotations from a JSON Response using MapKit. I've figured out some basic ways to plot out map points, but I"m not sure entirely what MapKit is expecting for map points. In my JSON response my struct is

Code Block // MARK: - Business
struct Business: Codable, Identifiable {
  let id, alias, name: String
  let coordinates: Center
}
struct Center: Codable {
  let latitude, longitude: Double
}

Then my code looks like this, but I think I'm using CLLocationCoordinate2DMake incorrectly.

Code Block    @State var yelpbusinessdataMap: WelcomeBusiness? = nil
   var body: some View {
    Map(coordinateRegion: $region,
      interactionModes: MapInteractionModes.all,
      showsUserLocation: true,
      userTrackingMode: $userTrackingMode,
      annotationItems: yelpbusinessdataMap?.businesses ?? []
    )
    { places in
      var new2DCoord = CLLocationCoordinate2DMake(places.coordinates.latitude, places.coordinates.longitude)
      MapAnnotation(
        coordinate:
          new2DCoord,
        anchorPoint: CGPoint(x: 0.5, y: 0.5)
      ){
        Circle()
          .stroke(Color.green)
          .frame(width: 44, height: 44)
      }
    }

I tried using coordinate: places.coordinates,, but I get the following compiler error

Cannot convert value of type 'Center' to expected argument type 'CLLocationCoordinate2D'

Answered by OOPer in 641681022

but I think I'm using CLLocationCoordinate2DMake incorrectly.

You should better clarify the reason why you think so.
You are not showing many things in your code.

WelcomeBusiness
$region
$userTrackingMode

So, readers need to guess many things, it makes readers spend more time to find the right solution.

I assume you get error like Unable to infer complex closure return type; add explicit type to disambiguate on the line { places in.

You need to specify the return type of the closure as you have a local var (it should be let, but that's another thing).
But in SwiftUI, it is hard to specify the return type explicitly because there are so many opaque types are used.

To avoid this, you should better try to simplify the closure as to contain only one expression and no other statements or declarations.

Declare an extension some where in your project (not in any other types):

Code Block extension Center {
    var coordinate2D: CLLocationCoordinate2D {
        return CLLocationCoordinate2DMake(self.latitude, self.longitude)
        
    }
}

And use it like this:

Code Block     var body: some View {
        Map(coordinateRegion: $region,
            interactionModes: MapInteractionModes.all,
            showsUserLocation: true,
            userTrackingMode: $userTrackingMode,
            annotationItems: yelpbusinessdataMap?.businesses ?? []
        ) { business in
            MapAnnotation(
                coordinate:
                    business.coordinates.coordinate2D, //<-
                anchorPoint: CGPoint(x: 0.5, y: 0.5)
            ){
                Circle()
                    .stroke(Color.green)
                    .frame(width: 44, height: 44)
            }
        }
    }

If this does not work in your project, you may need to show more code.

Boost

Answer 1

OOPer OP

Oct ’20

Accepted Answer

but I think I'm using CLLocationCoordinate2DMake incorrectly.

You should better clarify the reason why you think so.
You are not showing many things in your code.

WelcomeBusiness
$region
$userTrackingMode

So, readers need to guess many things, it makes readers spend more time to find the right solution.

I assume you get error like Unable to infer complex closure return type; add explicit type to disambiguate on the line { places in.

You need to specify the return type of the closure as you have a local var (it should be let, but that's another thing).
But in SwiftUI, it is hard to specify the return type explicitly because there are so many opaque types are used.

To avoid this, you should better try to simplify the closure as to contain only one expression and no other statements or declarations.

Declare an extension some where in your project (not in any other types):

Code Block extension Center {
    var coordinate2D: CLLocationCoordinate2D {
        return CLLocationCoordinate2DMake(self.latitude, self.longitude)
        
    }
}

And use it like this:

Code Block     var body: some View {
        Map(coordinateRegion: $region,
            interactionModes: MapInteractionModes.all,
            showsUserLocation: true,
            userTrackingMode: $userTrackingMode,
            annotationItems: yelpbusinessdataMap?.businesses ?? []
        ) { business in
            MapAnnotation(
                coordinate:
                    business.coordinates.coordinate2D, //<-
                anchorPoint: CGPoint(x: 0.5, y: 0.5)
            ){
                Circle()
                    .stroke(Color.green)
                    .frame(width: 44, height: 44)
            }
        }
    }

If this does not work in your project, you may need to show more code.

0

Answer 2

robevans OP

Oct ’20

Thank you. I'll be sure to do better in my posts in the future.

0