Patterns

Design patterns tell us how to structure classes and objects to solve certain problems
It is common for libraries and frameworks to make use of design patterns in their implementation.
Built around the key OO concepts: abstraction, inheritance, polymorphism, encapsulation

Encapsulate what varies or changes
Have composition over inheritance
Program to interfaces not implementations
Classes should be open for extension but closed for modification.

Patterns show you how to build systems with good OO design qualities

compound pattern ??

Pattern Categories

Creational	Object	Factory
Involve object instantiation with a way of decouplying a client from the objects it needs to instantiate	Object	Builder
	Object	Prototype
	Object	Singleton

Behavioural	Object	Chain of Responsibility
How classes and object interact and distribute responsibility	Object	Command
	Class	Interpreter
	Object	Iterator
	Object	Mediator
	Object	Memento
	Object	Observer
	Object	State
	Object	Strategy
	Class	Template Method
	Object	Visitor

Structural	Class	Adapter
Let you compose classes or objects into larger structures	Object	Bridge
	Object	Composite
	Object	Decorator
	Object	Facade
	Object	Flyweight
	Object	Proxy