Object Oriented Software Engineering   View all facts   Glossary   Help

subject > pattern > design pattern > player-role

player-role
subject			fact

player-role	has definition A pattern in found in class diagrams in which one class (the player) has several associated role classes. Instances of the role classes can change over the lifetime of a player
	has antipatterns merging all the properties and behaviours into the Player class which however, creates an overly complex class - much of the power of object orientation is lost
	has context A role is a particular set of properties associated with an object in a particular context. An object may play different roles in different contexts.
	has forces it is desirable to improve encapsulation by capturing the information associated with each separate role in a class but you want to avoid multiple inheritance you cannot allow an instance to change class
	has problem How do you best model players and roles so that a player can change roles or possess multiple roles?
	has related patterns Abstraction-Occurrence pattern
	has solution Create a «Player» class to represent the object that plays different roles. Create an association from this class to an abstract «Role» class, which is the superclass of a set of possible roles. The subclasses of this «Role» class encapsulate all the properties and behaviours associated with the different roles. If the «Player» can only play one role at a time, the multiplicity between «Player» and «Role» can be one-to-one, otherwise it will be one-to-many.
	is a subtopic of 6.4 - The Player-Role Pattern
	is an instance of design pattern
design pattern	has name
	has references one or more references which indicate who developed or inspired a pattern
	should be illustrated using a simple diagram
	should be written using a narrative writing style
pattern	should be as general as possible
	should be described in an easy-to-understand form so that people can determine when and how to use it
	should contain a solution that has been proven to effectively solve the problem in the indicated context

Next design pattern: proxy    Up: design pattern    Previous design pattern: observer