The overlay objects currently associated with the map view.
- iOS 4.0+
- macOS 10.9+
- tvOS 9.0+
This property contains the union of all overlays at the different levels of the map. The objects in this array must adopt the
MKOverlay protocol. If no overlays are associated with the map view, the value of this property is an empty array.
The order of the objects in this array does not necessary reflect their visual order on the map.