fix(ios): enforce ItemFeatureEvents conformance at compile time

Removed fatalError/assertionFailure stubs from ItemView base class and
dropped its ItemFeatureEvents conformance. Each *Impl subclass now
conforms to ItemFeatureEvents directly, making a missing override a
compiler error. MapViewImpl casts through the @objc boundary with
preconditionFailure to catch any future subclass that omits the
conformance.

Author: ajakka

ios/ArrowViewImpl.swift

@@ -3,7 +3,7 @@ import Foundation
 
 import heresdk
 
-@objcMembers public class ArrowViewImpl: ItemView {
+@objcMembers public class ArrowViewImpl: ItemView, ItemFeatureEvents {
 
   var mapArrow: MapArrow?
 
@@ -19,7 +19,7 @@ import heresdk
     didSet { updateFeature() }
   }
 
-  public override func updateFeature() {
+  public func updateFeature() {
     guard geoPolyline.count > 1 else { return }
     let coords = toCoordinatesList(raw: geoPolyline)
     guard coords.count > 1 else { return }
@@ -39,7 +39,7 @@ import heresdk
     }
   }
 
-  public override func removeFeature() {
+  public func removeFeature() {
     if let old = mapArrow {
       parentMap?.mapScene.removeMapArrow(old)
     }

ios/Helpers/ItemView.swift

@@ -8,18 +8,10 @@ public protocol ItemFeatureEvents {
 }
 
 @objc(ItemView)
-public class ItemView: UIView, ItemFeatureEvents {
-  
+public class ItemView: UIView {
+
   weak public var parentMap: MapView?
-  
-  public func updateFeature() {
-    fatalError("updateFeature() must be overridden in subclasses")
-  }
-  
-  public func removeFeature() {
-    fatalError("removeFeature() must be overridden in subclasses")
-  }
-  
+
   public func assignToMap(map: MapView) {
     parentMap = map
   }

ios/MapViewImpl.swift

@@ -58,13 +58,19 @@ import heresdk
 
   // Called by MapView.mm when a child ItemView is mounted
   @objc public func addItemView(_ itemView: ItemView) {
+    guard let feature = itemView as? ItemFeatureEvents else {
+      preconditionFailure("\(type(of: itemView)) must conform to ItemFeatureEvents")
+    }
     itemView.assignToMap(map: mapView)
-    itemView.updateFeature()
+    feature.updateFeature()
   }
 
   // Called by MapView.mm when a child ItemView is unmounted
   @objc public func removeItemView(_ itemView: ItemView) {
-    itemView.removeFeature()
+    guard let feature = itemView as? ItemFeatureEvents else {
+      preconditionFailure("\(type(of: itemView)) must conform to ItemFeatureEvents")
+    }
+    feature.removeFeature()
   }
 
   public func onTap(origin: Point2D) {

ios/MarkerViewImpl.swift

@@ -2,7 +2,7 @@ import Foundation
 
 import heresdk
 
-@objcMembers public class MarkerViewImpl: ItemView {
+@objcMembers public class MarkerViewImpl: ItemView, ItemFeatureEvents {
 
   var currentMapMarker: MapMarker?
 
@@ -22,7 +22,7 @@ import heresdk
     didSet { updateFeature() }
   }
 
-  public override func updateFeature() {
+  public func updateFeature() {
     guard let urlString = image["uri"] as? String,
           let url = URL(string: urlString)
     else {
@@ -66,7 +66,7 @@ import heresdk
     }.resume()
   }
 
-  public override func removeFeature() {
+  public func removeFeature() {
     if let oldMapMarker = currentMapMarker {
       parentMap?.mapScene.removeMapMarker(oldMapMarker)
     }

ios/PolygonViewImpl.swift

@@ -3,7 +3,7 @@ import Foundation
 
 import heresdk
 
-@objcMembers public class PolygonViewImpl: ItemView {
+@objcMembers public class PolygonViewImpl: ItemView, ItemFeatureEvents {
 
   var currentMapPolygon: MapPolygon?
 
@@ -27,7 +27,7 @@ import heresdk
     didSet { updateFeature() }
   }
 
-  public override func updateFeature() {
+  public func updateFeature() {
     var mapPolygon: MapPolygon?
 
     if geoCoordinates.count > 2 {
@@ -60,7 +60,7 @@ import heresdk
     }
   }
 
-  public override func removeFeature() {
+  public func removeFeature() {
     if let oldMapPolygon = currentMapPolygon {
       parentMap?.mapScene.removeMapPolygon(oldMapPolygon)
     }

ios/PolylineViewImpl.swift

@@ -3,7 +3,7 @@ import Foundation
 
 import heresdk
 
-@objcMembers public class PolylineViewImpl: ItemView {
+@objcMembers public class PolylineViewImpl: ItemView, ItemFeatureEvents {
 
   var mapPolyline: MapPolyline?
 
@@ -48,7 +48,7 @@ import heresdk
     didSet { updateFeature() }
   }
 
-  public override func updateFeature() {
+  public func updateFeature() {
     guard geoPolyline.count > 1 else { return }
 
     let coords = toCoordinatesList(raw: geoPolyline)
@@ -87,7 +87,7 @@ import heresdk
     }
   }
 
-  public override func removeFeature() {
+  public func removeFeature() {
     if let old = mapPolyline {
       parentMap?.mapScene.removeMapPolyline(old)
     }