whenFromState

whenFromState<E, K>(stateKey: K, fn: EntryListener<E & { from: FactoryKeyedState<E["machine"]["states"], K>; }>): (ev: E) => void

Defined in: factory-machine-hooks.ts:139

Creates an entry listener that triggers when the event’s from.key matches the given state key.

Type Parameters

Type Parameter	Description
E extends FactoryMachineEvent<any>	FactoryMachineEvent type
K extends any	State key type

Parameters

Parameter	Type	Description
stateKey	K	The state key to match against from.key
fn	EntryListener<E & { from: FactoryKeyedState<E["machine"]["states"], K>; }>	EntryListener to invoke when matched

Returns

An entry listener for the specified state key

(ev: E): void

Parameters

Parameter	Type
ev	E

Returns

void

Example

setup(machine)(
  effect(whenFromState("Idle", handleLeaveIdle)),
);

Source

Useful for running logic when leaving a specific state in a state machine.

export const whenFromState = <
  E extends FactoryMachineEvent<any>,
  K extends E["from"]["key"],
>(
  stateKey: K,
  fn: EntryListener<E & { from: FactoryKeyedState<E["machine"]["states"], K> }>
) => when<E>((ev) => ev.from.key === stateKey, fn);