Design practice

Software Design Essentials

Design patterns, SOLID, clean and hexagonal architecture and domain-driven design: how to structure code so it stays easy to change.

7 lessons1 h 15 minIntermediate

Start How to learn design patterns View curriculum

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What you'll learn

0 of 7 lessons complete

How to learn design patternsStart What patterns are, the three families, a map of the classic catalogue, and a practical way to learn them without over-engineering.9 minQuizExercise
The SOLID principlesFive guidelines for classes and modules that are easy to understand, extend and test, with before-and-after examples.12 minQuizExercise
Creational patterns: Factory, Builder, SingletonWays to create objects without hard-wiring the exact class: factories, builders, prototypes and why Singleton is usually a last resort.9 minQuizExercise
Structural patterns: Adapter, Decorator, Facade, ProxyHow to compose objects and wrap existing code so pieces fit together, add behaviour and hide complexity.10 minQuizExercise
Behavioural patterns: Strategy, Observer, Command, StatePatterns for how objects cooperate: swapping algorithms, reacting to events, turning actions into objects and changing behaviour with state.11 minQuizExercise
Clean and hexagonal architectureKeep business rules independent of frameworks, databases and the web: the dependency rule, layers, and ports and adapters.11 minQuizExercise
Domain-driven design essentialsA shared language, bounded contexts, entities, value objects, aggregates and domain events: modelling complex business software.12 minQuizExercise

Who this is for

Developers who can write working programs and want to structure them well: for larger codebases, for reviews and for design interviews.

After this course you will be able to

Learn design patterns efficiently, and know when not to use them
Apply the SOLID principles to spot and fix rigid, fragile code
Recognise and use the common creational, structural and behavioural patterns
Organise an application with clean and hexagonal architecture
Model a business domain with domain-driven design concepts

How a lesson works

Interactive diagram
See how each component connects, then run a request through it.
Plain-words toggle
Switch between the technical explanation and a plain-language one.
Practice design
Change a design of your own in the builder and see how it holds up.
Quiz and exercise
Test your understanding before moving on.

Go deeper

These lessons are written from scratch. The books below are excellent next reads.

Design Patterns: Elements of Reusable Object-Oriented Softwareby Gamma, Helm, Johnson and Vlissidesthe original catalogue of 23 patterns
Clean Architectureby Robert C. Martinthe dependency rule and architecture boundaries
Domain-Driven Designby Eric Evansthe book that introduced the approach; Vaughn Vernon's 'Domain-Driven Design Distilled' is a shorter start
Refactoring Guru: design patterns catalogueby Refactoring Gurufree explanations and examples of each pattern