Wait for a redux action to finish dispatching

Question

I have the following action creator:

export function scrolltoNextItem(item) {   return (dispatch, getState) => {     dispatch(appendItem(Item));     dispatch(       scrollToNextIndex(         getState().items.length - 1       )     )   } } 

Problem is that scrollToNextItem runs before appendItem has finished and the scroll position ends up being incorrect. I can prove this is the case by adding a setTimeout to make the execution of the script wait for the next tick before running scrollToNextItem:

export function scrolltoNextItem(item) {   return (dispatch, getState) => {     dispatch(appendItem(Item));     setTimeout(() => {       dispatch(         scrollToNextIndex(           getState().items.length - 1         )       )     }, 0);   } } 

How can I wait for the appendItem action to finish? In standard react land I would just use the setState callback:

this.setState({something: 'some thing'}, () => {   console.log('something is set'); }); 

But dispatch doesn't provide any callback functionality.

Answer 1

You can always wrap appendItem into a promise and pass dispatch as an argument to it

const appendItem = (item, dispatch) => new Promise((resolve, reject) => {   // do anything here   dispatch(<your-action>);   resolve(); } 

Then you can call it like this from scrolltoNextItem

export function scrolltoNextItem(item) {   return (dispatch, getState) => {     appendItem(Item, dispatch).then(() => {       dispatch(         scrollToNextIndex(           getState().items.length - 1         )       )     })   } }