README.md

vuex-cancellable-actions

This repository provides a wrapper around your vuex actions to allow the cancellation of an ongoing action. For the moment the only API function implemented is takeLatest which automatically cancels every past actions as soon as a new instance of the action is dispatched.

Usage

Wrap all your actions with makeCancellable and use the takeLatest wrapper around actions that should not be run in parallel.

new Vuex.Store({
  …
  actions: makeCancellable({
    action1: takeLatest(async function ({ commit, dispatch }, data) {
      dispatch('action2', data.subData)
      commit('commit1', data)
    }),
    action2: function (data) {
      commit('commit2', data)
    },
  })
})

Use case

After triggering an async action (let's name it action1), you may want to cancel it because a more recent action (action2) has occured and you don't want "action1" to keep on committing to the store while "action2" is also commiting. This could indeed lead to an inconsistent store.

To make things a bit less abstract let's consider the following scenario. Your vuejs application is loading and displaying a bunch of books and these books are filtered based on the menu selected by the user (e.g. read VS unread books). You have defined an action like:

async loadBooks ({ commit }, booksState) {
  const data = await apiCall(booksState)
  commit('setBookList', data)
}

If the number of read books is large, the API call may take longer to respond when fetching read books compared to when fetching unread books. Consequently, if the user switches quickly between the two menus, the following actions will be triggered:

dispatch('loadBooks', 'read')
// and a few ms later
dispatch('loadBooks', 'unread')

But since the API call is slower for read books, the order of commits will be reversed and the store will not reflect the user's latest action.

commit('setBooksList', unreadBooksData)
// and a few ms later
commit('setBooksList', readBooksData)

In this case it would be interesting to be able to cancel loadBooks, read as soon as loadBooks, unread is received to avoid the second commit. This is exactly what this library provides.