MEPX
Chapter 7 of 10All chapters
  1. 1Objects and classes
  2. 2Encapsulation
  3. 3Inheritance
  4. 4Polymorphism
  5. 5Composition over inheritance
  6. 6Design principles
  7. 7Design patterns
  8. 8State and mutation
  9. 9Testing object code
  10. 10When not to use it

Chapter 7 of 10

Design patterns

Named solutions to recurring shapes.

A few worth knowing

Strategy swaps an algorithm behind an interface. Adapter makes one interface look like another. Observer notifies interested parties. Factory decides which type to create.

  • Patterns are vocabulary first: they let two people discuss a design quickly.
  • Singleton is the one that causes the most trouble, because it hides a global.

Do not go looking

Patterns should be recognised in code that already needs them, not imposed in advance. Applying a pattern to a problem that does not have it adds indirection and nothing else.