I don't use anything in particular. I do have a dispatcher and event-based state updates, but I'm not sure why I'd need more than that.

Hello everyone, question : in :will-update, how to access the previous state of component ? The state I receive in this hook in the new state.

In React.js, it does receive the new state as well, but you can access the old state with this.state. https://reactjs.org/docs/react-component.html#componentwillupdate

I found (rum/state (:rum/react-component state)). I think this is what I want.

For those interested, it returns a Volatile. Be sure to deref if you want to access the values.