COMP 310
Fall 2017

Lec07: Designing a Ball

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Ballworld Design


Design patterns as expressions of CS principles:

Why are there only a few types of bridges in use today?  There are only 4-6 different types of bridges, depending on whoe you ask:  See for instance:. or

Connexions Lens on Design Patterns


Design Pattern CS Principle(s)
Union Polymorphism, inheritance
Composite Recursive data structures
Visitor Decoupled data and algorithms
Strategy Delegation to abstract processes/behaviors with known semantics
Command Delegation to abstract processes/behaviors with unknown semantics
State Dynamic reclassification -- objects that have changeable states and hence changeable behaviors.   Also, encapsulation barriers to decouple changes.
Model-View-Controller Dcomposition of a system into decoupled modules
Adapter Use of indirection layers for decoupling and communication via syntatic translations
Intepreter Data-driven algorithms, polymorphic dispatching, and recusion.
Factory Abstraction of the creation process of an entity
Template Concrete process involving abstract behaviors.
Singleton Uniqueness
Null Object Concept of "zero" (something that represents nothingness)
Observer-observable Decoupled communications from a single sender to multiple receivers.
Decorator Encapsulation barriers/indirection layers to intercept and modify processing paths.
Flyweight Resource pooling

To look for design patterns in the problem is to look for the underlying CS prinicples that are driving it.   The design patterns and the abstract notions that they represent comprise the "chunks" into which a problem is decomposed in order to understand it -- "Abstract decomposition"


HW02 homework instructions



© 2017 by Stephen Wong