Book of the Week: Design Patterns

30 Mar 2015

This week, I take a look at Design Patterns: Elements of Reuseable Object-Oriented Software, which is often recommended to new programmers. When you start out as a programmer, your main concern is writing code that accomplishes a task. As you write more and more code, you notice that you need to do the same things over and over again. You notice patterns. Then you begin to isolate and identify things by giving them names. When you starting talking to other programmers, you need some common vocabulary. Design Patterns provides that common vocabulary. 24 Design Patterns Purpose	Design Pattern	Aspects That Can Vary
Operation	Abstract Factory	families of product objects
	Builder	how a composite object gets created
	Factory Method	subclass of object that is instantiated
	Prototype	class of object that is instantiated
	Singleton	the sole instance of a class
Structural	Adapter	interface of an object
	Bridge	implementation of an object
	Composite	structure and composite of an object
	Decorator	responsibilities of an object without subclassing
	Façade	interface to a subsystem
	Flyweight	storage costs of objects
	Proxy	how an object is accessed; its location
Behavioral	Chain of Responsibility	object that can fulfill a request
	Command	when and how a request is fulfilled
	Interpreter	grammar and interpretation of a language
	Iterator	how an aggregate’s elements are accessed, traversed
	Mediator	how and which objects interact with each other
	Memento	what private information is stored outside an object, and when
	Observer	number of objects that depend on another object; how the dependent objects stay up to date
	State	states of an object
	Strategy	an algorithm
	Template Method	steps of an algorithm
	Visitor	operations that can be applied to object(s) without changing their class(es)