Monsters design

This design appeared in the 2004 exam.

Design notes

• This is an incomplete framework of classes that track the behaviour of Monsters. More types of Monster are expected to be added later.
• The DarkPlaces in which Monsters live and the Humans on which they prey are also modelled.
• EtherealMonsters are bodiless; they can walk through walls.
• CorporealMonsters have bodies; they can bite().
• A Demon can exist only by possessing some other monster. It takes over control of the possessed Monster.
• A Mimic pretends to be another CorporealMonster. Usually, it just forwards messages to the original monster, but it can vary behaviour if it wants to.
• A Vampire can change its style between behaving like a person and behaving like a bat.
• A Lycan is a Human turned into a hairy Monster. When its fullmoon() method is invoked, it tries to hunt a Human and bite() him/her. The bite() of a Lycan turns the victim into another Lycan of the same type.
• Monsters lurk in DarkPlaces: UnderBeds, in Wardrobes and Dungeons. If a Dungeon is a Labyrinth, it can have other Dungeons inside it, but it cannot if it is a Cavern.
• Monsters and Humans can use an Explorer subclass to look around inside DarkPlaces.
• Constructors, getters and setters, and many methods have been omitted from the diagram. Make reasonable assumptions where necessary and state them.

Spot the GoF pattern

• Composite: Labyrinth, Dungeon
• Decorator: Lycan, Human (Robert thinks this is not a decorator)
• Decorator: Demon, Monster
• Factory Method: Lycan
• Proxy: Mimic
• Strategy: Vampire, VampireStyle
• Template Method: Lycan
• Visitor: Explorer, Dark Place