CODEWITHSUNDEEP
reactjsreduxreact-redux
Sean
Sean

Reputation: 647

Does useSelector automatically unsubscribe the component from store updates when it is unmounted?

I was looking through the source code for useSelector as part of the react-redux library.

I was wondering if useSelector automatically unsubscribes components from redux store updates when the component unmounts, similar to using the unsubscribe function returned by calling store.subscribe in Redux? Or if another component changes that piece of state, will this still be subscribed to such changes?

Upvotes: 1

Views: 1126

Answers (1)

markerikson
markerikson

Reputation: 67469

Yes, useSelector explicitly unsubscribes from the store when the component unmounts. Per https://github.com/reduxjs/react-redux/blob/v7.2.2/src/hooks/useSelector.js#L81 :

  useIsomorphicLayoutEffect(() => {
    function checkForUpdates() {
      try {
        const newSelectedState = latestSelector.current(store.getState())

        if (equalityFn(newSelectedState, latestSelectedState.current)) {
          return
        }

        latestSelectedState.current = newSelectedState
      } catch (err) {
        // we ignore all errors here, since when the component
        // is re-rendered, the selectors are called again, and
        // will throw again, if neither props nor store state
        // changed
        latestSubscriptionCallbackError.current = err
      }

      forceRender()
    }

    subscription.onStateChange = checkForUpdates
    subscription.trySubscribe()

    checkForUpdates()

    return () => subscription.tryUnsubscribe() // unsubscribes here
  }, [store, subscription])

Upvotes: 4

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