How to define the order of overlapping MKAnnotationViews?

Under iOS 11 the implementation of displayPriority broke all the solutions which use bringSubviewToFront or zPosition.

If you override the annotation view's CALayer, you can wrestle control of zPosition back from the OS.

class AnnotationView: MKAnnotationView {

    /// Override the layer factory for this class to return a custom CALayer class
    override class var layerClass: AnyClass {
        return ZPositionableLayer.self
    }

    /// convenience accessor for setting zPosition
    var stickyZPosition: CGFloat {
        get {
            return (self.layer as! ZPositionableLayer).stickyZPosition
        }
        set {
            (self.layer as! ZPositionableLayer).stickyZPosition = newValue
        }
    }

    /// force the pin to the front of the z-ordering in the map view
   func bringViewToFront() {
        superview?.bringSubviewToFront(toFront: self)
        stickyZPosition = CGFloat(1)
    }

    /// force the pin to the back of the z-ordering in the map view
   func setViewToDefaultZOrder() {
        stickyZPosition = CGFloat(0)
    }

}

/// iOS 11 automagically manages the CALayer zPosition, which breaks manual z-ordering.
/// This subclass just throws away any values which the OS sets for zPosition, and provides
/// a specialized accessor for setting the zPosition
private class ZPositionableLayer: CALayer {

    /// no-op accessor for setting the zPosition
    override var zPosition: CGFloat {
        get {
            return super.zPosition
        }
        set {
            // do nothing
        }
    }

    /// specialized accessor for setting the zPosition
    var stickyZPosition: CGFloat {
        get {
            return super.zPosition
        }
        set {
            super.zPosition = newValue
        }
    }
}

Ok, so for solution use method from MKMapViewDelegate

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views
 

In this method you should rearrange AnnotationView after it was added to mapKit View. So, code may looks like this:

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views {
   for (MKAnnotationView * annView in views) {
      TopBottomAnnotation * ann = (TopBottomAnnotation *) [annView annotation];
      if ([ann top]) {
         [[annView superview] bringSubviewToFront:annView];
      } else {
         [[annView superview] sendSubviewToBack:annView];
      }
   }

}

This works for me.