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DESIGN PATTERNS in Ruby

The Catalog of Ruby Examples

Creational Patterns

Abstract Factory

Abstract Factory

Lets you produce families of related objects without specifying their concrete classes.

Builder

Builder

Lets you construct complex objects step by step. The pattern allows you to produce different types and representations of an object using the same construction code.

Factory Method

Factory Method

Provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

Prototype

Prototype

Lets you copy existing objects without making your code dependent on their classes.

Singleton

Singleton

Lets you ensure that a class has only one instance, while providing a global access point to this instance.

Structural Patterns

Adapter

Adapter

Provides a unified interface that allows objects with incompatible interfaces to collaborate.

Bridge

Bridge

Lets you split a large class or a set of closely related classes into two separate hierarchies—abstraction and implementation—which can be developed independently of each other.

Composite

Composite

Lets you compose objects into tree structures and then work with these structures as if they were individual objects.

Decorator

Decorator

Lets you attach new behaviors to objects by placing these objects inside special wrapper objects that contain the behaviors.

Facade

Facade

Provides a simplified interface to a library, a framework, or any other complex set of classes.

Flyweight

Flyweight

Lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects, instead of keeping all of the data in each object.

Proxy

Proxy

Lets you provide a substitute or placeholder for another object. A proxy controls access to the original object, allowing you to perform something either before or after the request gets through to the original object.

Behavioral Patterns

Chain of Responsibility

Chain of Responsibility

Lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.

Command

Command

Turns a request into a stand-alone object that contains all information about the request. This transformation lets you parameterize methods with different requests, delay or queue a request's execution, and support undoable operations.

Iterator

Iterator

Lets you traverse elements of a collection without exposing its underlying representation (list, stack, tree, etc.).

Mediator

Mediator

Lets you reduce chaotic dependencies between objects. The pattern restricts direct communications between the objects and forces them to collaborate only via a mediator object.

Memento

Memento

Lets you save and restore the previous state of an object without revealing the details of its implementation.

Observer

Observer

Lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they're observing.

State

State

Lets an object alter its behavior when its internal state changes. It appears as if the object changed its class.

Strategy

Strategy

Lets you define a family of algorithms, put each of them into a separate class, and make their objects interchangeable.

Template Method

Template Method

Defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure.

Visitor

Visitor

Lets you separate algorithms from the objects on which they operate.