Creational design patterns

Abstract factory: Provide an interface for creating families of related or dependent objects without specifying their concrete classes

Builder: Separate the construction of a complex object from its representation so that the same construction process can create different representations

Factory Method: Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses

Prototype: Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype

Singleton: Ensure a class only has one instance, and provide a global point of access to it

Structural design patterns

Adapter: Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn’t otherwise because of incompatible interfaces

Bridge: Decouple an abstraction from its implementation so that the two can vary independently

Composite: Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly

Decorator: Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality

Façade: Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use

Flyweight: Use sharing to support large numbers of fine-graned objects efficiently

Proxy: Provide a surrogate or placeholder for another object to control access to it

Repository: The abstraction of data storage to allow for multiple different implementations where only one is selected but not known about by the repository user

Behavioral design patterns

Chain of responsibility: Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it

Command: Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undo-able operations

Interpreter: Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language

Iterator: Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation

Mediator: Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently

Memento: Without violating encapsulation, capture and externalize an object’s internal state so that the object can be restored to this state later

Observer: Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically

State: Allow an object to alter its behavior when its internal state changes. The object will appear to change its class

Strategy: Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it

Template method: Define the skeleton of an algorithm in a operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure

Visitor: Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates

Unit of work: This is a class that is responsible for keeping running modifications to commit to a repository in memory. When ready, the unit of work can be committed all in a single transaction. A unit of work can be thought of as a ledger/transaction for work done by a single request

Further reading

Read more on wikipedia or by buying the book by the gang of four Design Patterns: Elements of Reusable Object-Oriented Software