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technologies used: React Native / Expo / Firebase

I explain to you, I recover a list of key with my first onValue, in this one I forEach for each key and in this one I make another onValue in order this time to recover the information of the keys, but I realize that it creates a problem, one event calls another and it creates duplicate calls. Moreover I could not intervene on the second listening to delete it since it is only initialized locally, so how can I call this in the right way? thank you in advance for your answers, I'm new to react native with firebase!

Here is a snippet of the code:

useFocusEffect( // first time the screen is loaded, the gardener list is empty, so we need to get the gardener list from firebase

  React.useCallback(() => {
      setGardeners([])

      const gardenerRef = ref(db, 'users/' + auth.currentUser.uid + '/gardeners');
      const gardenerListener = onValue(gardenerRef, (snapshot) => {
          const data = snapshot.val();
          if (data != null) {
              setIsFirst(false)
              Object.keys(data).forEach(e => {
                  const temp = ref(db, 'gardeners/' + e);
                  onValue(temp, (snapshot) => {
                      const data = snapshot.val();
                      if (data != null && data.metadata != undefined) {
                          setGardeners(gardeners => [...gardeners, { id: e, name: data.metadata.name, isIrrig: data.irrig }]);
                      }
                  })
                  gardeners.length > 0 ? setCurrentGardener(gardeners[0].id) : setCurrentGardener("")
                  setC(currentGardener != "" ? currentGardener : "")
              })
          } else {
              setIsFirst(true)
          }
      })


and here is the way i turn off the event during disassembly, for me it looks correct, now if you think i did it wrong, don't hesitate.

return () => {
             setGardeners([])
             off(gardenerRef, gardenerListener)
             // console.log("unmounted")
         }
  }, []))


What I have tried:

I tried to take the second onValue out of the first, but without success I can't get access to my data, I also try to off it but I can't because the databaseReference and the listener are only initialized locally, and on React with javascript you cannot create a lateinit variable
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