Explain like I'm five · SW Eng

What is a GoF Design Pattern?

GoF design patterns, told as a story about a publishing house's formula book — proven solutions collected for each commonly repeated writing problem.

every writer reinvents how to plant a plot twist, from scratcheven though many books have already solved this same problem

Every writer reinvents how to plant a plot twist, from scratch.Even though many books have already solved this same problem.

everyone can just write it their own waythen every book's structure differs — confusingreinventing the method every time means writing with one never proven

A suggestion that everyone write their own way ends up making every book's structure different.Reinventing the method every time means writing with one never proven.

PROVEN WRITING FORMULAScreational — bringing a character to lifestructural — weaving chapters togetherbehavioral — how an event ripples outwardGoF design patterns = a formula book of proven solutions, one for each commonly repeated problemfour authors (the Gang of Four) organized the patterns into 23 formulas

GoF design patterns are a formula book of proven solutions for repeated problems.Four authors (the Gang of Four) organized the patterns into 23 formulas.

Find a proven formulachecking if the problem's already been solved
How to bring a character to lifehandled by creational patterns
How to weave chapters togetherhandled by structural patterns
How an event ripples outwardhandled by behavioral patterns
THREE FAMILIES OF PATTERNScreational — singleton, factory, etc.structural — adapter, decorator, etc.behavioral — observer, strategy, etc.23 formulas in totalmemorizing formulas alone doesn't make a good bookforcing a formula where it doesn't fit only makes the structure needlessly complicated

The formulas split into three families.Memorizing formulas alone doesn't make a good book.

a proven formula is faster than starting from scratchbut choosing which formula to use is still the writer's calldesign patterns are tools in hand — knowing when to use them is still the writer's own judgment

Choosing which formula to use is still the writer's own judgment.Patterns are tools in hand — when to use them is still up to the writer.

In one breath

GoF design patterns = a book of 23 proven formulas, one for each commonly repeated problem.

GoF (Gang of Four) refers to the four authors who catalogued these patterns, split into 23 patterns across three categories: creational (how objects get made), structural (how classes and objects are composed), and behavioral (how objects share work and communicate). Each pattern is a named, reusable solution to a specific design problem — what matters more than memorizing the patterns themselves is judging which one fits a given situation.

When grown-ups say it

Gang of Four
The four authors who first compiled the formula book. Catalogued the 23 patterns.
Creational Patterns
Formulas for bringing a character to life. Includes singleton, factory method, and more.
Structural Patterns
Formulas for weaving chapters together. Includes adapter, decorator, and more.
Behavioral Patterns
Formulas for how an event ripples outward. Includes observer, strategy, and more.
Software Architecture
The structural blueprint for the whole book. A much larger unit than a design pattern.
Reengineering (3R)
Tracing a lost original backward to rebuild it. These formulas can be applied while rewriting. → tracing back a lost original to rebuild it
Refactoring
Keeping the plot but polishing the sentence structure. A pattern can be the destination refactoring moves toward.
UML Diagrams
The design map drawn before writing. Also used to draw a pattern out visually. → the design map drawn before writing
Next story
Splitting the Thick Book into Small Volumes →
Want another term as a picture book? Request →