Replace Conditional with Polymorphism

Goal

Each case becomes a class implementing a shared interface; dispatch happens once via virtual call.

Before the refactoring

switch (event.kind) {
  case 'click': return onClick(event);
  case 'key':   return onKey(event);
}

After the refactoring

event.handle(); // ClickEvent and KeyEvent each implement handle()

Savings

Adding a new case is one new class; the type system tells you what's missing.

Note

If only one switch on the type code exists, polymorphism is overkill — wait for the second or third repeat before extracting subclasses.