Why is setState asynchronous?
github.com
github.com
This gives me flexibility to structure the code how I want. You can have the separate "controller" classes deal with operations (like API requests) and the "react class" mostly deals with display - it delegates actions to the controller and retrieves data from the controller. This can promote code reuse, notably certain components can share the controller class (not instance) when you have similar logic.
As a more general principle, I like react just fine as a way to express the DOM in a functional way and for its magic of figuring out just what parts of the actual DOM must be updated; but I don't really care about how React wants me to write code in other aspects, like where and how I should manage my data.
Reducers are composable, so you can actually end up with pretty clean code in large codebases
Most (presentational) components will load its needed data from a container component (through connect(), or other higher order components we developed). So for example, a given `user` object, could have its data in a chat component, or an analytics view, or a settings profile. The reducers aren't generally concerned with how the data is used, just that its available to anyone who asks.
As far as localized state goes (like a form), we took a page from reduxForm (and we use reduxForm) - if there were times we needed to use setState a lot (for example, we had a query builder and chart components), we built a higher order component (like connect), where you would pass the props you need, and that component would figure out how to query it and make it available in the redux state. Again this meant you could create a "query object" from one component, that was theoretically available to any other component (as part of the Redux tree), if they asked.
All in all, I never considered any sort of 1:1 relationship between state and components. I had state, and the components decided what state they needed and rendered themselves appropriately. This was a fairly complex SPA that had real time chat, analytics and CRM-like features, there were 100s of components.
Our codebase was far more robust from the Angular version we had rewritten it from a year ago (a component crashing didn't bring down the whole app), and the concerns for every component tended to be self-discoverable (we were able to hire interns to start hacking on it within 2-3 days, after they wrapped their head around redux). I'll admit it took me sometime to understand the benefits of Redux, and there was a lot of ugly boilerplate until we started using higher order components, however "brittle" and "messy" is the last words I'd use to describe the codebase.
Think of the classic case showcase of redux being used with immutable structures to implement a page-wide undo easily. There's a certain amount of state that could be burried deep in components that doesn't need to be in the global redux store.
Sure, your undo might not now be an exact representation of the historical state of the page, but the state that counts is still re-created, and that's the state that you can decide to put into redux.
Redux makes available state that is required globally, like the contents of your todo list or other properties that must persist as you navigate a web app. Components will store their own state for their specific requirements.
I suggest reading up on redux use cases to find out more before dismissing it entirely.
I've certainly seen a number of people in the community who insist that you _must_ keep everything in Redux, and that you should probably only use functional components along with that. I can understand why people might want to do that, as it means there's more state in the Redux store for traceability, UI output becomes highly predictable, etc. However, I would say that approach is too dogmatic and over-opinionated. It's a valid choice if you want to go there, but not something that should be enforced across the ecosystem or taught to learners. Class components, functional components, Redux store state, and React component state are all tools with specific use cases, and throwing any of them away is unnecessarily limiting your toolbox.
(Might not have been exactly what you were asking, but given how frequently this topic comes up, I wanted to put that clarification out there.)
I don't necessarily recommend using this project specifically, as I don't devote any time to maintaining it. There's a whole next-generation of how I think it should work that I haven't gotten around to persuing. But I mention it to back the overall approach. It makes UI refactors extremely easy, as components are generally not responsible for any dependencies of their descendant subtree, with the exception of some parent-child interactions.
I haven't tried it, but I think Freactal [2] also seems to allow for this sort of separation of concerns.
That said, it is best used as you describe it: a store that holds all the application state and manages API requests, and then any time it updates, any components observing this store will be forceUpdated
What is controversial is the (incorrect) notion that developers shouldn't use state. There are some perfect use cases for state and people somehow got the idea that they shouldn't use it (as opposed to not using it as the first tool, necessarily, if props can be used).
However, instead of calling forceUpdate(), I was under the impression that componentWillReceiveProps(props) was more efficient?
Perhaps I'm wrong on that one, though... Just that forceUpdate() is an approach that is officially encouraged against.[0]
[0] - https://reactjs.org/docs/react-component.html#forceupdate
One example is the text I’m currently typing - that would only be relevant at a component level, maybe including an adjoining word counter. Once I hit reply, though, it becomes part of the application state.
An exception would be if I was continuously storing what was typed for offline use - in that case it’s always application state.
I think this blog post highlights the frustrating viral nature that is async functions:
http://journal.stuffwithstuff.com/2015/02/01/what-color-is-y...
- async, continuation passing style code
- async with delineated continuations to make snippets look synchronous which aren't actually
- cooperative multi-tasking (co-routines with async I/O under the covers)
- threading (preemtible multitasking)
There are times, of course, when your code is very serial, and then you really do benefit from co-routines/threads. For example, PuTTY's implementation of the SSH version exchange, key exchange, and user authentication protocols, is one HUGE C function that is actually running as a co-routine which cooperates with the UI side, with async I/O under the covers. The PuTTY approach is wonderful for that particular case: those parts of the SSH protocols are extremely serial, and the resulting serial-looking code is very very easy on the eyes (so much so that it makes up for the enormity of the function that implements it!). So it pays to be able to reach for co-routines sometimes, but not always, and I'd say not even most of the time.
Programmers today simply have to be prepared to deal with everything-is-async codebases, and they should be prepared to create codebases where everything is async from day zero.
There's nothing special about "async" per se. What about people writing OS code in the 90s? They didn't even hear about async and the "sync" was invented for the sake of easier control over the time shared between processors (remember all of our implementations of processes in OSs are CPS-style, where they just give up the control over their stack if run for more than X ms).
Other thing I do recently consider a lot is asynchronicity between machines: 1) receive a request 2) send a database request 3) return an error if database request had timed out ...) etc. Having a language that spans several systems, enveloping time, execution redundancy contraints and ensuring data passed is not garbage is something that would be novel.
There's only so much the compiler can do for you. At some point you have to bear some of the cognitive load of state compression (which is really all async is about).
Multi-processing was great, but it doesn't scale to today's world, and neither does multi-threading. It doesn't matter in the least that those two technologies allow the programmer to write serial-looking code that does not execute serially. Those technologies cannot compress program state embodied in the call stacks and heap, therefore they do not scale (because they consume too much memory, have worse cache footprints and higher resident set size, involve heavy-duty context switching, and so on).
In terms of actual novelty in this space in computer science, I don't believe there's been anything new since the 80s. Everything that seems to be new is an old idea rediscovered, or a new take on an old idea, so either way not new at all.
CPS -> least implicit state.
Process -> most implicit state.
In between those two there are a few options, but nothing is a panacea, and ultimately CPS is an option you have to be prepared to use.
Less implicit state -> explicit state, which you can compress well because you understand its semantics.
Less state -> less load for the same work -> more work can be done.
In some contexts (e.g., the UI) this is a very big deal, which is why GUIs are async.
In a world of fast CPUs, slow memory, distributed computing (whether client/server or peer-to-peer), remote function as a service, ..., asynchrony is a hard requirement.
The GUI event model has been with us since... even before the days of X11. Asynchrony in the UI is and long long has been a hard requirement. Users hate synchronous UIs, and rightly so.
Asynchrony is also difficult. But it's not like sync + threads is a panacea -- it's not because threads are way too heavy-duty. Better to deal with the pain than to deny the need.
Build only what you need today, and prepare for what your employer says you will need tomorrow. Anything else is like saying everybody should buy a jeep in case they move to the countryside.
Async brings its own costs. Unless your employer benefits, you are costing them money by giving them features they don’t need.
I’ve worked with plenty of valuable apps not using async. If the requirements change such that async becomes the best way to solve the problem, that’s something the business would decide at that point.
Experience is helpful here.
When I have to write C I try to at least write thread-safe C close to something I could expose as a library. I've had too many cases where I or someone else wrote code they NEVER thought would be needed as a library, therefore took all sorts of liberties, and then suddenly there was a need for a library to do what said code was doing. Oops. I've run into fewer instances of sync code that turns out should really have been async and where adding threads isn't good enough, but I've still run into some.
This isn't about functionality -- this is about scalability. When you know you need to scale, you have to think ahead about it.
But then along comes a developer who says “we must build this app with async so we can scale”. Suddenly the junior devs build an absolute mess because they don’t know how to work effectively with async. So a few seniors get involved. Then the project runs out of cash.
Sure, some projects benefit from async and some fundamentally require it. But not all of them, I doubt even the vast majority of them.
You only need to scale when you’re successful, and most applications are not successful.
If you just want it not to block using the page then you can just chain the sync code into a bunch of async callbacks. For actually parallelizing tasks that weren't before, it can be harder, but in my experience still not a full rewrite. It is much harder for larger applications in other contexts like the migration of Firefox to Quantum, though, yes.
Still though, JS is a mess.
The linked blog post doesn't seem to agree with you. He goes on to talk about Promises and async/await—both features of modern javascript—which he describes as "nice":
> Async-await is nice, which is why we’re adding it to Dart
He does finish by talking about Go's concurrency model, which he describes as being more "beautiful", but I still wouldn't confuse "it's nice" for "its a mess".
Also, the line about Java doing it better seems to be a joke.