observe
fun SupplyChainModel.Demand.observe(observer: DemandLifecycleObserver): DemandStateChangeListener(source)
Attach observer to this demand. Returns the underlying DemandStateChangeListener so callers can remove the subscription later via SupplyChainModel.Demand.removeStateChangeListener.
fun SupplyChainModel.Order.observe(observer: OrderLifecycleObserver): OrderStateChangeListener(source)
Attach observer to this order. Returns the underlying OrderStateChangeListener so callers can remove the subscription via SupplyChainModel.Order.removeStateChangeListener.