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Back to Outline 18 - Professional Ethics, Revisited. On to Outline 20 - Good Design, Revisited.

Summary

We consider the use of design patterns in software design.

Related Pages

Overview

• Refactoring, revisited.
• Design patterns.
• The GoF list of patterns.

Administrivia

• What did you do/learn without me?

Upcoming Work

• Readings for Wednesday: SaaSbook Chapter 11
• Reading Journal for Wednesday (due Tuesday at 8pm)
  • Subject: Reading Journal for Class 20 (Your Name)
  • What does the SOLID acronym stand for?
  • In your own words, what is a design pattern? What is an antipattern?
  • Which design principle or pattern did you find the most relevant to your CSC 322 project or other prior experience with object-oriented programming? Explain the pattern and why you chose it.
  • Which design principle or pattern did you find the most confusing? Explain it as best you can and say where you got confused.
  • As always, better questions were stolen from JLND.

Good Things to Do

Academic

• Public Events Concert Tuesday Night

Peer

Other

Refactoring, Revisited

• As we noted, we use refactoring to improve code, particularly code that smells bad. We'll consider a few of the bad smells you identified and consider how to approach them.
• Nearly identical code (within a procedure):
• Nearly identical code (similar procedures):
• Too many parameters:
• Magic numbers:
• Complex conditionals:
• Code that is never executed:
• Too-long methods:

Design Patterns

• Inspired by C. Alexander's work on Architecture, A Pattern Language.
• Leading OO-programmers/designers looked at common software architecture tasks/problems and came up with a taxonomy of common solutions to those problems.
• Valuable in (at least) two ways
  • For novice programmers, provides better approaches to tasks that they don't realize are old.
  • For experienced programmers, provides a language to talk about approaches.
• There are growing movements to write "patterns" (and "anti-patterns") for many different classes of problems. There are even teaching patterns.
• Most folks at Grinnell believe that you apply patterns loosely; they are intended as a way to help you think, rather than strict strategies.

Patterns

Creational

• Abstact Factory
• Factory Method
• Singleton
• Prototype
• Builder

Structural

• Adapter
• Proxy
• Facade
• Bridge
• Decorator
• Composite
• Flyweight

Behavioral

• Template Method
• Strategy
• Observer
• Iterator
• Visitor
• State
• Chain of Responsibility
• Mediator
• Interpreter
• Command

More Smells

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