Guidelines for maintainable object-oriented design.
Single responsibility, Open-closed, Liskov substitution, Interface segregation and Dependency inversion guide maintainable designs. They reduce coupling, make extensions safer and improve testability. Apply with judgement, not dogmatically.
Swapping a database implementation without changing business logic follows DIP.
SOLID principles are guidelines that keep object-oriented designs maintainable as they grow, so they are common in code reviews.
Guidelines for maintainable object-oriented design.
SOLID principles are guidelines that keep object-oriented designs maintainable as they grow, so they are common in code reviews.
A class should have one reason to change, so each class focuses on one job.
High-level code should depend on abstractions rather than concrete details, which makes components easier to replace and test.
Typical applications include splitting a large class that handles both storage and display, adding new payment methods without editing existing code and replacing a concrete dependency with an interface to make testing easier.
Study "Encapsulation, inheritance and polymorphism" first (topic 35 of 104 in Software & Computing). It covers the groundwork this topic builds on.
High cohesion low coupling. Depend on abstractions. Dependency injection.
Swapping a database implementation without changing business logic follows DIP.
The next topic is "Design patterns", which builds directly on this one.
It is classed as Beginner in Software & Computing (topic 36 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.