split(trigger, cases)

Pattern matching method, splits trigger unit (event, effect or store) into several events, which fire upon trigger matches its comparator function.

Arguments

  1. trigger (Event | Effect | Store): Event, Effect or Store unit-trigger.
  2. cases (Object): Schema of cases, which uses names of resulting events as keys, and comparator function((value) => Boolean)

Returns

(Object) - Object, having keys, defined in cases argument, plus __(two underscores) - which stands for default (no matches met) case.

Example 1

import {createEvent, split} from 'effector'
const message = createEvent()
const messageByAuthor = split(message, {
bob: ({user}) => user === 'bob',
alice: ({user}) => user === 'alice',
})
messageByAuthor.bob.watch(({text}) => {
console.log('[bob]: ', text)
})
messageByAuthor.alice.watch(({text}) => {
console.log('[alice]: ', text)
})
message({user: 'bob', text: 'Hello'})
// => [bob]: Hello
message({user: 'alice', text: 'Hi bob'})
// => [alice]: Hi bob
/* default case, triggered if no one condition met */
const {__: guest} = messageByAuthor
guest.watch(({text}) => {
console.log('[guest]: ', text)
})
message({user: 'unregistered', text: 'hi'})
// => [guest]: hi

Try it

Note: the only first met match will trigger resulting event

Example 2

import {createEvent, split} from 'effector'
const message = createEvent();
const {short, long, medium} = split(message, {
short: (m) => m.length <= 5,
medium: (m) => m.length > 5 && m.length <= 10,
long: (m) => m.length > 10,
});
short.watch((m) => console.log(`short message '${m}'`));
medium.watch((m) => console.log(`medium message '${m}'`));
long.watch((m) => console.log(`long message '${m}'`));
message("Hello, Bob!")
// => long message 'Hello, Bob!'
message("Hi!")
// => short message 'Hi!'

Try it