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• Metaobject: Used to create other objects (similar to a class, but an object)

• Prototype object: a specialized metaobject that creates new objects by copying itself

• Singleton object: only instance of its class for the lifetime of the program

• Filter object: receives a stream of data as its input and transforms it into the object's output

A common anti-pattern is the God object, an object that knows or does too much.

Design Patterns: Elements of Reusable Object-Oriented Software is a famous book published in 1994 by four authors: Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. People often call them the "Gang of Four". The book talks about the strengths and weaknesses of OOP and explains 23 common ways to solve programming problems.

These solutions, called "design patterns," are grouped into three types:

• Creational patterns (5): Factory method pattern, Abstract factory pattern, Singleton pattern, Builder pattern, Prototype pattern

• Structural patterns (7): Adapter pattern, Bridge pattern, Composite pattern, Decorator pattern, Facade pattern, Flyweight pattern, Proxy pattern

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