archive-gh-me/react-rxjs
1
0
Fork 0
mirror of https://github.com/re-rxjs/react-rxjs.git synced 2025-12-08 18:01:51 +00:00
Code Issues Projects Releases Wiki Activity

perf(core): avoid unnecessary calls to setState

Browse Source
This commit is contained in:
Josep M Sobrepere 2020-10-14 17:55:18 +02:00
parent ccf81ed603
commit c01cd43cb0
1 changed files with 15 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
packages/core/src/internal/useObservable.ts
View File

@ -1,4 +1,4 @@
import { useEffect, useState } from "react"
import { useEffect, useState, useRef } from "react"
import { SUSPENSE } from "../SUSPENSE"
import { EMPTY_VALUE } from "./empty-value"
import { Observable } from "rxjs"
@ -8,19 +8,11 @@ export const useObservable = <O>(
getValue: () => O,
): Exclude<O, typeof SUSPENSE> => {
const [state, setState] = useState(getValue)
const prevStateRef = useRef<O | (() => O)>(state)
useEffect(() => {
let prevVal: O | typeof SUSPENSE = EMPTY_VALUE
let err: any = EMPTY_VALUE
const onNext = (value: O | typeof SUSPENSE) => {
if (value === SUSPENSE) {
setState(getValue)
} else if (!Object.is(value, prevVal)) {
setState(value)
}
prevVal = value
}
let syncVal: O | typeof SUSPENSE = EMPTY_VALUE
const onError = (error: any) => {
err = error
setState(() => {
@ -28,11 +20,20 @@ export const useObservable = <O>(
})
}
let subscription = source$.subscribe(onNext, onError)
let subscription = source$.subscribe((val) => (syncVal = val), onError)
if (err !== EMPTY_VALUE) return
if (prevVal === EMPTY_VALUE) onNext(SUSPENSE)
const set = (val: O | (() => O)) => {
if (!Object.is(val, prevStateRef.current)) {
setState((prevStateRef.current = val))
}
}
if (syncVal === EMPTY_VALUE) set(getValue)
const t = subscription
subscription = source$.subscribe(onNext, onError)
subscription = source$.subscribe((value: O | typeof SUSPENSE) => {
set(value === SUSPENSE ? getValue : value)
}, onError)
t.unsubscribe()
return () => subscription.unsubscribe()