Batching actions

[tshelburne]

I needed to be able to mark specific actions as "skipped" so that a larger action could encapsulate smaller ones without notifying subscribers of incoherent state. I created redux-skip-by-action for this purpose - unit tests are pending, QA tests passing, and any feedback would be really appreciated.

Thanks.

[gaearon]

In my view this hurts predictability.
What is the use case compared to just firing one action instead of many?

[gaearon]

Instead, the “Redux approach” to this would be to create a batching action creator:

function batchActions(...actions) {
  return {
    type: 'BATCH_ACTIONS',
    actions: actions
  };
}

// usage
store.dispatch(
  batchActions(
    doSomething(),
    doSomethingElse()
  )
);

and a higher order reducer:

function enableBatching(reducer) {
  return function batchingReducer(state, action) {
    switch (action.type) {
    case 'BATCH_ACTIONS':
      return action.actions.reduce(batchingReducer, state);
    default:
      return reducer(state, action);
    }
  }
}

// usage
let store = createStore(enableBatching(reducer));

[gaearon]

We might want to add this to the docs..

[fubhy]

I solved this with a middleware that acts on action yielding generators.

[tshelburne]

@gaearon I have a situation where I need to set a property (action creator 1), validate via external service the new value of the property (action creator 2), get the initial state via external service of another object based on that property, and then set that object in the state as well (action creator 3), and then finally validate the entirety of the new state via another external service (action creator 4). The place where things fell apart for me was the external service parts - if I allow subscribers to receive a notification after action 1, they receive an incoherent state, but I kept finding myself pushed to make the async calls in the reducers in order to move in the direction you described.

If I'm reading your suggestion right, I basically need to create a list of actions to run at the end of a promise chain that gets dispatched all at once. Rather than dispatching actions to the store to get updated state, I use getState initially and run my reducer manually against that "copy" to build the list of simple object actions that will ultimately be run in the store. Does this sound right?

This all felt a bit manual to me before, but I think that does pretty drastically improve the predictability of things.

[tshelburne]

@gaearon That's a much better solution - thanks for the direction, feel free to close this.

[tshelburne]

Also, note that the arguments in your higher order reducer for the passthrough are reversed - should be reducer(state, action)

[tshelburne]

I also noticed that it's better to use batchingReducer recursively to enable combining batched actions into larger groups.

function enableBatching(reducer) {
  return function batchingReducer(state, action) {
    switch (action.type) {
    case 'BATCH_ACTIONS':
      return action.actions.reduce(batchingReducer, state);
    default:
      return reducer(state, action);
    }
  }
}

[gaearon]

Good points. Want to publish this as a package?

[tshelburne]

Will do - I'll take care of it tonight and ping you.

[tshelburne]

Added to GH and published on npm - let me know your thoughts: https://github.com/tshelburne/redux-batched-actions

[gaearon]

12661e5