persist with sync storage

Hi,

I’m using react-native-mmkv as a replacement to asyncstorage,

react-native-mmkv is a sync library, but when using it in the persist middlewar, it doesn’t rehydrate.

This is what I had to write to get it to work

export const storage: StateStorage = {
  getItem: async (key: string): Promise<string | null> => {
    const reply = MMKV.getString(key)
    return Promise.resolve(reply ?? null)
  },
  setItem: async (key: string, value: string): Promise<void> => {
    MMKV.set(key, value)
    Promise.resolve()
  },
}

but ideally, it should work synchronously

export const storage: StateStorage = {
    getItem: (key: string): string | null => {
      const reply = MMKV.getString(key)
      return reply ?? null
    },
    setItem: (key: string, value: string): void => {
      MMKV.set(key, value)
    },
  }
}

I’ve read a bit about the issue here and I was wondering it https://github.com/pmndrs/zustand/pull/455 fixes the issue, or maybe I should look elsewhere for a fix ?

[austinried]

Thanks for that link @AnatoleLucet, I’m not sure how I’d use hasHydrated in my case since what I want to do is call a function on the state once hydration has been finished, and that only seems to allow me to check if it’s been finished. I also tried to subscribe to onFinishHydration but wasn’t able to get that to work, I’m guessing because I was subscribing to it too late and hydration was already done.

But, I did read more into that and learned that sync storage is actually finished when the state is created, so in my case I just switched to calling the function on the state I wanted directly in my splash screen component instead of waiting for hydration and trying to call it in onRehydrateStorage/setting my own hydrated prop on the state, and now it’s working fine.

[jbrodriguez]

The error param is not set in onRehydrateStorage if that’s what you meant.

I’ll try a clean cache, etc. and retry setRehydrated, to check if it was something odd happening.