Repeated Switches

Apply refactorings

Replace Conditional with Polymorphism

Referenced by patterns

HumanAgent

Symptom

The same switch (or if/else chain) over a type code appears in multiple places — adding a new case means hunting them all down.

Goal

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

Smellier version

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

Fresher version

event.handle(); // ClickEvent, KeyEvent, DragEvent each implement handle()

Example source: Illustrative example written for this site, not a quotation from any source.

Pressure

Dispatch logic is duplicated across the codebase; new cases are easy to miss; the type-code couple amplifies.

Tradeoff

Replacing the switch with polymorphism scatters dispatch across classes; adding a new case is one new file, but understanding the full dispatch surface now requires reading several.

Relief

Adding a new case is one new class; the compiler and tests surface what's missing.

Trap

Polymorphism worship — a switch with two stable cases becomes a class hierarchy of two trivial subclasses, paying class-hierarchy overhead with no flexibility return.