Hands-On Design Patterns with Kotlin

Back to our bases

HQ is a special building that can produce other buildings. It keeps track of all the buildings it had built up until now. The same type of building can be built more than once:

class HQ {    val buildings = mutableListOf<Building<*, Unit>>()    fun buildBarracks(): Barracks {        val b = Barracks()        buildings.add(b)        return b    }    fun buildVehicleFactory(): VehicleFactory {        val vf = VehicleFactory()        buildings.add(vf)        return vf    }}

You may be wondering what the star (*) means as regards generics. It's called a star projection, and it means I don't know anything about this type. It's similar to Java's raw types, but it's type safe.

All other buildings produce units. Units can be either infantry or armored vehicle:

interface Unit interface ...