标签:rop OLE function log init arguments options prope can
We can invoke a callback as a service when we enter a state in XState. This gives us the ability to trigger various functionality by responding to events sent to the service, and allows us to send events back to the parent machine.
We do this by writing a "callback handler" and setting it as the src
of our invoked service. A callback handler is a function that receives the current context
and the event
object that triggered the invocation. This function returns another function that receives two functions as arguments. A callback
function to send events to the parent machine, and an onEvent
function for the handler to respond to events sent to the handler.
The way events are sent to the callback handler is by utilizing the options
argument of the send
action creator. We identify where we send events to using the to
property, and setting the value to the id
of our service.
const handlerEchoCallback = (context, event) => { return (callback, onReceive) => { onReceive(e => { if (e.type === ‘FOO‘) { callback(‘ECHO‘); // call the ‘ECHO‘ action } }) } } const callbackMachine = Machine({ id: ‘callbackMachine‘, initial: ‘listening‘, states: { listening: { invoke: { src: handlerEchoCallback, id: ‘handlerEchoCallback‘ }, on: { SPEAK: { actions: send(‘FOO‘, { to: ‘handlerEchoCallback‘ }) }, ECHO: { actions: (context, event) => { console.log(‘echo‘, context, event); } } } } } })
[XState] Invoke Callbacks to Send and Receive Events from a Parent XState Machine
标签:rop OLE function log init arguments options prope can
原文地址:https://www.cnblogs.com/Answer1215/p/12222589.html