// Composition r01

One machine per entity

Don't try to fit ten orders into one machine. Spin up a fresh instance per row, and let each one run its own lifecycle independently.

Code

machineFor.ts

const OrderM = () => sm`
  cart 'pay' → paid 'ship' → done;
`;

const byId = new Map();
function machineFor(id) {
  if (!byId.has(id)) byId.set(id, OrderM());
  return byId.get(id);
}

Notes

Each entity carries its own state — no shared bag of flags, no row accidentally inheriting another's status. When the row's gone, drop its machine.