7 design patterns that explain 80% of the code you'll ever read.
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Singleton
One instance for the whole app.
Logger, config, DB pool.
Factory
Ask by name, get the right object back.
No hardcoded classes in your code.
Builder
Assemble a complex object step by step.
Ends with .build(). Think query builders.
Adapter
Makes incompatible interfaces work together.
Old XML in, new JSON out.
Decorator
Wrap an object to add behaviour.
Core stays untouched. Think middleware.
Observer
Change once, every subscriber is notified.
Event listeners, pub/sub.
Strategy
Swap the algorithm, not the caller.
Payment methods, sorting, routing.
Which one do you use most? 🔖