The Law of Demeter

The Law of Demeter, or the principle of least knowledge, states that a software component should have limited knowledge about the inner details of other components. More specifically, a component should not know about the internal details of another component.

Let us say there is a function that returns the city in the address of a person:

class Person(val name: String, val address: Address) {
    fun getAddressCity(): String {
        return address.city
    }
}
class Address(val city: String)

The Person class directly accesses the city property inside the Address class. The Person class should not have this knowledge, as this is a violation of the Law of Demeter.

This creates a coupling between Person and Address. The coupling dictates that if the city property changes its data type, then both classes will need to change. It also means that the code change is bigger than...