A Humorous Guide to 23 Classic Design Patterns Illustrated with Dating Analogies

Factory Method

The Factory Method separates client code from concrete product creation; the client asks a factory for a product (e.g., ordering chicken wings at a restaurant) without knowing the specific class that will be instantiated.

Builder

The Builder pattern isolates a product’s internal representation from its construction process, allowing step‑by‑step creation of complex objects (e.g., a multilingual "I love you" device with language‑specific buttons).

Abstract Factory

Abstract Factory defines an interface for creating families of related objects without specifying concrete classes, letting the client request a product (e.g., a hamburger) and letting the concrete factory decide the exact variant.

Prototype

Prototype creates new objects by cloning an existing prototype instance, enabling rapid duplication of pre‑written “love messages” for reuse.

Singleton

Singleton ensures a class has only one globally accessible instance, suitable when exactly one object (e.g., a “husband” role) is required.

Adapter

Adapter converts one interface into another expected by the client, allowing incompatible classes (e.g., a Cantonese speaker and a Mandarin speaker) to communicate through a mediator.

Bridge

Bridge decouples an abstraction from its implementation so they can vary independently, illustrated by combining greetings (morning, evening, compliment) with different contexts via composition.

Composite

Composite composes objects into tree structures to represent whole‑part hierarchies, enabling clients to treat individual items and compositions uniformly (e.g., a gift set of shirt, skirt, and bag).

Decorator

Decorator adds responsibilities to objects dynamically without altering their structure, akin to wrapping a photo in a decorative frame and box to enhance its presentation.

Facade

Facade provides a simplified high‑level interface to a complex subsystem, such as switching a camera to auto mode so a non‑expert can take photos easily.

Flyweight

Flyweight shares common intrinsic state among many fine‑grained objects while keeping extrinsic state separate, exemplified by storing reusable message templates and appending a recipient’s name.

Proxy

Proxy supplies a surrogate that controls access to a real subject, filtering repetitive greetings before forwarding other messages to the user.

Chain of Responsibility

Chain of Responsibility passes a request along a linked list of handlers until one processes it, similar to passing a love note through successive classmates.

Command

Command encapsulates a request as an object, separating the invoker from the executor and allowing operations such as undo or queuing.

Interpreter

Interpreter defines a grammar for a language and provides an evaluator that interprets sentences according to that grammar, like following a scripted dating guide.

Iterator

Iterator provides a way to access elements of an aggregate sequentially without exposing its underlying representation.

Mediator

Mediator centralizes complex communications and control between related objects, reducing direct dependencies (e.g., settling debts among friends through a neutral party).

Memento

Memento captures and externalizes an object’s internal state so it can be restored later without violating encapsulation.

Observer

Observer defines a one‑to‑many dependency so that when the subject changes state, all its observers are automatically notified.

State

State allows an object to alter its behavior when its internal state changes, appearing as if the object changed its class.

Strategy

Strategy defines a family of algorithms, encapsulates each one, and makes them interchangeable, enabling selection of different courting tactics.

Template Method

Template Method defines the skeleton of an algorithm in a base class while allowing subclasses to refine specific steps.

Visitor

Visitor lets you define new operations on elements of an object structure without changing the classes of the elements.