Subclassing `MKMapItem` resulting in Fatal error

I would like the MKMapItem returned from MKLocalSearch to contain an "altitude" property. In order to achieve this, I've decided to create a subclass for MKMapItem.

class MapItemGeoSpatial: MKMapItem {
    var altitude: Measurement<UnitLength>
    
    public init(placemark: MKPlacemark, altitude: Measurement<UnitLength>) {
        self.altitude = altitude
        super.init(placemark: placemark)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

While the above implementation compiles, it results in a fatal error when attempting to initialise MapItemGeoSpatial.

Fatal error: Use of unimplemented initializer 'init()' for class 'MapItemGeoSpatial'

The above error occurs during the super.init(placemark:) call.

The altitude property is set by me (the source of this value is not relevant to this discussion, but it is determined by extracting the coordinates from MKMapItem) via the designated initialiser. I understand that MKLocalSearch has nothing to do with altitude, but I, as the client, found it desirable to contain this information when it is passed to other areas of my project. This is the primary reason why I chose to subclass MKMapItem, in an attempt to "inherit" all it's functionality and introduce my own functionality.

The flow diagram for this process is- MKLocalSearch -> MKMapItem  -> Determine altitude using coordinates from MKMapItem -> Initialise MapItemGeoSpatial.

I can create an override init() for the above class, but this will require me to initialise the altitude property, which is not specified for this initialiser. Initialising altitude by specifying a dummy variable (eg. 0) overcomes this issue, but appears to be a poor workaround. Making altitude optional is another workaround, but this is not a direction I wish to take. I'm aware that MKMapItem inherits from NSObject and I'm curious if this relation has an influence on the above observation. I would like to-

1. Understand the root cause behind this issue and
2. Determine if subclassing MKMapItem is a viable solution to the problem mentioned at the start of this post