Issues with the object-oriented design
Two of the issues that we saw with the object-oriented design were directly related to each other, and are the result of Swift being a single-inheritance language. Remember a single-inheritance language is a language that limits a class to having not more than one super-class.
An object-oriented design with a single-inheritance language, such as Swift, can lead to bloated superclasses because we may need to include functionality that is needed by only a few of the subclasses. This leads to the second issue related to Swift being a single-inheritance language, which is the inheritance of functionality that a type does not need.
In our design, we had to include the functionality for all three terrain types because the vehicle types may be able to move or attack in any of the terrain types. Having this extra functionality may lead to errors in our code if we are not careful. It is really easy to accidently create a class like this:
class Infantry: Vehicle...
