Add an optional 'callback' to dispatch

[mhodgson]

Called when all listeners have resolved.

This enables a dispatch caller to run a callback once all changes from an action have been flushed and rendered (in my case to the DOM via React).

I didn't include a promise implementation here since I don't know what people's preferences are.

Thoughts about this? I have a specific use case around DOM selection binding that this enables.

See reduxjs/react-redux#208 for related change to react-redux.

[mhodgson]

@gaearon @ellbee Any thoughts here? This is a non-breaking change with no effect on the existing API and enables callbacks that need to occur after all updates are complete (i.e. inspecting selection state, taking screenshots, re-enabling listeners, etc.).

[just-boris]

If you want to get this working, you should pass callback through all store decorations in compose method.

[gaearon]

I don't think we want to get this in.
The store acts like a very simple event emitter.
We don't want to make it more complex.

I don't know what a better solution would look like but it shouldn't involve Redux.
It's similar to how you wouldn't modify Rx or EventEmitter to fix a similar problem.
It's just not their concern.

[mhodgson]

@gaearon as far as I can tell there is no way to use redux for this use case then. Why is having a callback for when a dispatch is 'complete' outside of the scope of Redux?

[gaearon]

Because dispatch is synchronous. It doesn't make sense to add an async callback to a synchronous method. Asynchrony is an implementation detail of your subscribers and should be dealt with on their level—whether in React Redux, React itself, or via some other means.

[mhodgson]

Thanks for the explanation. I think I see a path forward by adding a decorator outside of @connect and overriding the listener trigger in Connect.