- 🐌 If a subscriber/listener subscribes to a service that is already running, it will now receive the current state upon subscription. #814
- 🆙 The new
escalate()action creator escalates custom error events to a parent machine, which can catch those in theonErrortransition:
import { createMachine, actions } from 'xstate';
const { escalate } = actions;
const childMachine = createMachine({
// ...
// This will be sent to the parent machine that invokes this child
entry: escalate({ message: 'This is some error' })
});
const parentMachine = createMachine({
// ...
invoke: {
src: childMachine,
onError: {
actions: (context, event) => {
console.log(event.data);
// {
// type: ...,
// data: {
// message: 'This is some error'
// }
// }
}
}
}
});- ❓ You can now specify
undefinedas the first argument formachine.transition(...), which will default to the initial state:
lightMachine.transition(undefined, 'TIMER').value;
// => 'yellow'-
🤝 Services (invoked machines) are now fully subscribable and can interop with libraries that implement TC39 Observbles like RxJS. See https://xstate.js.org/docs/recipes/rxjs.html for more info.
-
🆔 When a service is invoked, it has a uniquely generated
sessionId, which corresponds to_sessionidin SCXML. This ID is now available directly on the state object to identify which service invocation the state came from:state._sessionid#523 -
⚙️ The original
configobject passed toMachine(config)(orcreateMachine(config)) is now the exact same object reference in the resultingmachine.configproperty. -
🎰 The
createMachine()factory function now exists and is largely the same asMachine(), except with a couple differences:- The generic type signature is
<TContext, TEvent, TState>instead of<TContext, TStateSchema, TEvent>. - There is no third argument for specifying an initial
context. Use.withContext(...)on the machine or return a machine with the expectedcontextin a factory instead.
- The generic type signature is
-
🛑 Event sent to a stopped service will no longer execute any actions, nor have any effect. #735
-
🚸 The invoked actors are now directly available on
state.children. -
✍️ Plain strings can now be logged in the
log()action creator:
entry: log('entered here', 'some label')- 🚄 Transitions are now available on
state.transitions, which is an array of transition objects that detail exactly which transitions were enabled to transition to this state. This will be ignored in serialization. - ⏩ New action creator:
forwardTo()https://xstate.js.org/docs/guides/actions.html#forward-to-action - ➕ Assigners now have a third
metaargument passed in, which contains meta data such as thestateand the originalaction - *️⃣ New event type: the wildcard! https://xstate.js.org/docs/guides/transitions.html#wildcard-descriptors
const quietMachine = Machine({
id: 'quiet',
initial: 'idle',
states: {
idle: {
on: {
WHISPER: undefined,
// On any event besides a WHISPER, transition to the 'disturbed' state
'*': 'disturbed'
}
},
disturbed: {}
}
});
quietMachine.transition(quietMachine.initialState, 'WHISPER');
// => State { value: 'idle' }
quietMachine.transition(quietMachine.initialState, 'SOME_EVENT');
// => State { value: 'disturbed' }- 📲 New action creator:
respond()https://xstate.js.org/docs/guides/actions.html#respond-action - ✅ New typechecking feature: Typestates https://xstate.js.org/docs/guides/typescript.html#typestates-coming-soon
- 📄 SCXML event metadata is now available on
state._eventand also in action/guard/etc. meta under_event. https://www.w3.org/TR/scxml/#InternalStructureofEvents