[storage] update all storage engines to use promise instead of callback

[rt2zz]

In 5.0.0-beta.13 we converted from callback to promise. This is going to be a painful change as all storage engines will need to be updated, however better to bite the bullet now as longer term it will make the code easier to maintain and less bytes.

[williamoliveira]

I made a little adapter to keep using old callback based storage engines before they update

const promisefy = fn => (...args) => new Promise((resolve, reject) => {
  fn(...args, (err, result) => (err ? reject(err) : resolve(result)))
})

const storageAdapter = storage => ({
  getItem: promisefy(storage.getItem),
  setItem: promisefy(storage.setItem),
  removeItem: promisefy(storage.removeItem),
  getAllKeys: promisefy(storage.getAllKeys),
})

[rt2zz]

thank you for sharing this, mind if we ship this utility in redux-persist? im thinking it could live at import storageCallbackAdapter from 'redux-persist/lib/integration/storageCallbackAdapter'

[williamoliveira]

Sure, just one thing, I actually had to bind every method for a class based storage because I was getting an error in a place it was using this, not sure if it is the correct thing to do tho, my js abilities only go so far

// ...
const storageAdapter = storage => ({
  getItem: promisefy(storage.getItem.bind(storage)),
  setItem: promisefy(storage.setItem.bind(storage)),
  removeItem: promisefy(storage.removeItem.bind(storage)),
  getAllKeys: promisefy(storage.getAllKeys.bind(storage)),
})

[leethree]

I just wrote a storage engine based on react-native-fs that supports both Promise and callback. Would love to hear your feedback:

https://github.com/leethree/redux-persist-fs-storage

[rt2zz]

awesome! added to the readme https://github.com/rt2zz/redux-persist/tree/v5