如何從類中為 EnvironmentObject 設置值？

Question

我想從 Delegate 類為 EnvironmentObject 設置值。

struct AppleMapView: UIViewRepresentable {
  @EnvironmentObject var mapViewViewModel: MapViewViewModel
  let mapViewDelegate = MapViewDelegate()
  class MapViewDelegate: NSObject, MKMapViewDelegate {
    func mapView(_ mapView: MKMapView, didChange mode: MKUserTrackingMode, animated: Bool) {
     // This is where I want to set value to EnvObj
     **mapViewViewModel.mode = mode**
    }
  }
}

這就是我想要做的。

我的代碼給出錯誤

Instance member 'mapViewViewModel' of type 'AppleMapView' cannot be used on instance of nested type 'AppleMapView.MapViewDelegate'

所以，我嘗試引用委托類：

MapViewDelegate(vm: mapViewViewModel)這沒有編譯錯誤，但是當我運行代碼時它出錯了

A View.environmentObject(_:) for MapViewViewModel may be missing as an ancestor of this view.: file /BuildRoot/Library/Caches/com.apple.xbs/Sources/Monoceros_Sim/Monoceros-39.4.3/Core/EnvironmentObject.swift, line 55 ```

兩者都不起作用。 我該如何修復我的代碼？

Answer 1

它以不同的方式工作，它需要讓你的MapViewDelegate作為MapViewDelegate協調AppleMapView ，如下所示

struct AppleMapView: UIViewRepresentable {
  @EnvironmentObject var mapViewViewModel: MapViewViewModel

    func makeUIView(context: Context) -> MKMapView {
        let mapView = MKMapView()
        mapView.delegate = context.coordinator // << your delegate
        return mapView
    }

    func makeCoordinator() -> MapViewDelegate {
        MapViewDelegate(self)   // << will be created for you
    }

  class MapViewDelegate: NSObject, MKMapViewDelegate {
    var owner: AppleMapView
    init(_ owner: AppleMapView) {
      self.owner = owner
    }
    func mapView(_ mapView: MKMapView, didChange mode: MKUserTrackingMode, animated: Bool) {
       owner.mapViewViewModel.mode = mode // << now you have access to owner props
    }
  }
}