Recoil – A state management library for React

Keajs has been amazing I upgraded from 0.28 to 2.0 yesterday and had 1 small issue, had to delete [actions.] from the reducers.

I use to use just Redux and it was such a pain.

I know you have added even more features in v2 that I will need to take advantage of.

If you need to add examples https://versoly.com/ is what I built on top of keajs.

Has about 8 logic stores that have 100s of actions, thunks, reducers and some interesting selectors.

Never made any OpenSource lib, but I always had that gut feeling you are talking about here:

"Unfortunately, even for me, a library author, it's hard to evaluate all of them properly. It would take just too much time and you never know where the real problems in any framework lay before you get neck-deep in code. And then you're too far to switch to another framework anyway."

Putting that aside, to me RxJS and especially Cycle.js are "1 abstraction level above" React & friends. (Cycle can be used via React.)

What do you think about these?

Well, I know that on one tool we saw a 20x or so speedup compared to using Redux. This is because Redux is O(n) in that it has to ask each connected component whether it needs to re-render, whereas we can be O(1).

useReducer is equivalent to useState in that it works on a particular component and all of its descendants, rather than being orthogonal to the React tree.

I think if you can model something with pure functions, you should. That's the approach we try to take for asynchronous processes: just a pure function that you happen to evaluate on some other process. This obviates the need for things like sagas. So I agree with you there I guess.

If you post an example of what you don't think it could handle I will tell you how we would handle it.

> I still haven't found anything that beats Redux on its own without thunks or sagas

There was a period in the early days of Redux where MobX [0] (and, perhaps to a lesser extend, MobX State Tree [1]) was the main competitor to Redux that I used to hear about. They both seem to be actively developed, but I don't hear so much about them any more. Have you ever look at either of them?

BTW I am 100% with you on Sagas.

[0] MobX https://mobx.js.org/README.html#introduction [1] MobX State Tree: https://mobx-state-tree.js.org/intro/philosophy

Having worked many years on mid to large scale React apps, I must say: In most cases component state (or useSate) and context works just fine.

Why is everyone so eager to add third party state libraries from the getgo? In most projects, Redux doesn't add net value.

For complex state flows we use Kea JS. https://kea.js.org/

The library has been around for a while and reduces a lot of boilerplate.

Is also used by some quite big names.

One viable alternative for thunks and sagas that I came up with is using async functions and explicitly getting/setting state: https://github.com/riptano/statium#viewcontroller

Still a long list of chores to improve API, tooling, etc but very performant and battle tested.

Agreed. But Redux loop is nice. Kinda like reframe for JavaScript.

Mind describing why you dislike thunks

Its a huge issue in all of those also. It just presents itself differently. JSP -- every click has to post or query param change re-renders the page. This gets hugely cumbersum with tree stateor anything other than basic switches. In a lot of ways its the one way data flow we all want in react. For a lot of pages its easy. Same with React, However complex state is so difficult to do in JSP you really can't write the apps we write today.

I would say React's state management is its great success, rather than its `functionalness` or its reactivity. No other UI framework (QT|WinForms|MOTIF|GTK) really ever handled state well.

Don't have experience with ASP or JSP, but managing state in React is vastly superior than iOS. Having a defined place to keep your data, and your view automatically refresh when it changes is the gold standard in user interface design. iOS does not easily have this kind of functionality, forcing people to use all sorts of messy techniques that are hard to follow and maintain.

The main "Apple approved" tools for user interface and state management are CoreData and UIKit. Both are imperative, mutable, and overall difficult to work with. This might be subjective, but I always notice just how poorly Apple's own apps work. There is always some button that is stuck in the wrong state, some feature that doesn't do what its supposed to, and some broken animation when views reload (I'm looking at you Podcast app). I can't know why, but my hunch is that Apple engineers are forced to use unwieldy patterns and technologies like CoreData, MVC, and UIKit, and are drowning in a sea of unmaintainable code.

As a response to the inadequate tools Apple provides, big industry leaders have stepped up and rolled their own declarative solutions. IGListKit from Instagram is a prime example of a declarative user interface solution thats vastly superior to Apple's. Going even further, Facebook basically ported React into iOS with ComponentKit.

It took Apple a good decade, but they are finally giving us these types of tools as well with SwiftUI. However, judging from its low adoption, so far they have not managed to fully get things right.

React is not a complete framework more of a templating engine and nothing more, it allows you to use any state management you want. It also makes it easy to add to existing projects without requiring rewrite of everything from the ground up.

> What is it about React that state management is such a such a hassle?

I'm not sure it's a hassle, just different schools of thought.

> This is not the case in other frameworks.

None of the examples you mention are reactive AFAIK. The point of React is that the UI is a function of the state. How exactly that is accomplished is where those different schools of thought come into the picture.

React has fantastic tools for state management built-in. The difficulty is a particular flavor of state management: data that lives in the "global" scope but can be used locally in components in a reactive fashion. We have some good tools for doing this but they all have drawbacks, hence the experimentation.

FWIW I've never seen a really great solution for this in any JavaScript framework. I read it as a sign of React's maturity that this is a focus.

Perhaps it's due to React's architecture of one way data flow?

If you want even cooler try overmind:

https://overmindjs.org

But Recoil is slightly different, designed to be “component first” essentially. Not global. It’s how my own personal mobx based library works. But this one likely has concurrent mode baked in.

The term 'atom' is a clojure-ism, that's where both I and reframe get it from.

I’m working on a detailed comparison for the docs. Thanks for the feedback!

It’s actually designed to make server rendering easy. We’ll add a guide about this eventually. Atoms aren't global singletons: their values are scoped to React trees.

Lol, MobX literally uses the concept of atoms under the hood.

If you update multiple atoms within a React batch, they will be updated at the same time, just as with React local state. You don't need to wrap the changes in anything to have them occur together.

In other words, this updates both of the atoms together:

  const [a, setA] = useRecoilState(atomA);
  const [b, setB] = useRecoilState(atomB);
  ...
  onClick={() => {
    setA(a => a + 1);
    setB(b => b + 1);
  }}

If the new values of multiple atoms are interdependent on each others' current values, it's possible to update multiple atoms together using the transactional/updater/function form, but we need to add a nicer interface for doing this. Coming soon! The nicer interface would probably look something like this:

  const update = useTransactionalUpdate([atomA, atomB]);
  ...
  onClick={() => {
    update(([a, b]) => [a + b, b - a]);
  }}

It's then easy to make a hook that provides a reducer-style interface over a set of atoms. But now, unlike with Redux or useReducer, each atom still has its own individual subscriptions!

Recoil allows you to create atoms and selectors in loops without having to add an entire new Context.Provider component to the root of the React component tree, which would obviously not be viable since the entire tree would need to be torn down each time.

I'll experiment with this.