title | hide_title |
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Concurrency |
true |
In the basics section, we saw how to use the helper effects takeEvery
and takeLatest
in order to manage concurrency between Effects.
In this section we'll see how those helpers could be implemented using the low-level Effects.
import {fork, take} from "redux-saga/effects"
const takeEvery = (pattern, saga, ...args) => fork(function*() {
while (true) {
const action = yield take(pattern)
yield fork(saga, ...args.concat(action))
}
})
takeEvery
allows multiple saga
tasks to be forked concurrently.
import {cancel, fork, take} from "redux-saga/effects"
const takeLatest = (pattern, saga, ...args) => fork(function*() {
let lastTask
while (true) {
const action = yield take(pattern)
if (lastTask) {
yield cancel(lastTask) // cancel is no-op if the task has already terminated
}
lastTask = yield fork(saga, ...args.concat(action))
}
})
takeLatest
doesn't allow multiple Saga tasks to be fired concurrently. As soon as it gets a new dispatched action, it cancels any previously-forked task (if still running).
takeLatest
can be useful to handle AJAX requests where we want to only have the response to the latest request.