Discriminated Unions
Discriminated Unions (π solution)
π¨βπΌ Perfect implementation of discriminated unions!
π¦ This patternβdefining all possible states and using exhaustive
switch
statementsβis fundamental to functional programming. It's exactly how React,
Redux, and many modern libraries handle state.This pattern is extremely common in real applications:
- API states (loading, success, error)
- Form states (idle, submitting, submitted, error)
- Authentication (anonymous, authenticated, loading)
- Payment methods (card, PayPal, crypto)
The exhaustiveness check with
never ensures you can't forget to handle a case
when you add a new variant. TypeScript becomes your safety net!Notice how each function here is a pure transformation: it takes a state,
inspects it, and returns a result without side effects. This is the functional
patternβdata flows through functions, types guide your logic.