Without some global state management library like Redux, what would be a good way to pass the user around through my components? I'm using Firebase, so I'm imagining my top-level app component will be listening to auth changes and storing the user somewhere. Here are the options I've thought of:
Passing 'user' to each route in props (and on to children that need it)
Using a global object of my own
Using Context
1 seems like a hassle.
2 doesn't seem like the right way and like more of a hassle, wouldn't I have to listen for changes and set the user in my states? It's what they show in the React Router docs but I'm guessing that's just for simplicity's sake and not best practice.
3 seems like the best way to me but it seems like it's discouraged:
The vast majority of applications do not need to use context.
If you
want your application to be stable, don't use context. It is an
experimental API and it is likely to break in future releases of
React.
I would still say that you use context. It's the best way I have found to thread a common state throughout the react tree.
Even though they discourage it, all popular react libraries (including react-redux) use it big time. It's not going to be removed any time soon. And the use case seems very legit, provided you know what you are doing.
Related
I have a function that interacts with local state/hook that I want to be able to call from other distant component(s)
For instance, calling a React Apollo mutation that has local side-effects from the response in that component from other areas. Also keeping code DRY without duplicate the hook in everywhere its used, and setting global state that is only read in this one component.
Another similar use-case would be calling a refetch() from specific UI elements - like a button in a distant component (so refetchQueries would not be applicable here)
Let me know if additional clarity or a specific example would help.
Options I've considered:
EventBus: there seems to be little about event buses as a recommended approach. Most posts link to React recommending this in old docs from years ago. It seems feasible, potentially could even setup a pubsub with hooks, but I'm not sure if it's an anti-pattern. In Vue it is common.
Global State:, Context would seem to be overkill for such a specific and small use case, but I am already using an atomic state library. I could set an atom to hold the function on mount, and call the function from the atom where I want.
What would be some practical ways to do this? I'm curious as to other possible approaches, trade-offs, or insight into other implementations you may have used.
I may choose to put some states as component states, and I thought that's what useState() is for.
However, the book Learning React, O'Reilly, 1st Ed, 2nd Release, p. 185, said:
With Redux, we pull state management away from React entirely.
Also, in the official Redux website, the example "Real World" also even make isFetching a Redux state, instead of component state. (Its GitHub repo).
I also found that in some project in some company, coworkers seem to favor everything as Redux state even when it can be a component state.
For example, in that same book, p. 185, it said we even keep which messages is expanded or not into the Redux store. But which message is expanded, seems entirely local to this component and it has nothing whatsoever to do with other components at all. In the case of isFetching, as least I can understand it that what if the whole app wants to unite the isFetching of any component into a global spinner indicator.
This webpage also says:
The solution in idiomatic React – i.e., code that was written the way an experienced React developer would write it – is to have what's called a single source of truth, which is one master state for most if not all of your application, then send that state down as props to your child components.
be a pragmatic programmer: go for stateless components where possible
I don't quite understand it. How does it work? When a state can be a component state, would it be perfectly ok to put it as component state? Or in React / Redux, the rule is to make everything into a Redux state? (in such case, then what is useState() for?)
Update: I like #RemcoGerlich's answer, and I put two links as a comment under his answer. Those are official docs stating "Don't put all states into Redux".
It is an eternal discussion. There are several types of state that have their own best ways to solve them:
Navigation related state, to go to different "pages" or kinds of views in your application. For this, using the browser URL has many usability advantages, and using React Router is much more natural.
State retrieved from the backend through its API, this isn't really state of your frontend at all, you have a cache. For this a library like React Query is much more suited (it handles e.g. your "isFetching" state, as well as reloading things after a while).
Small bits of state that only have local significance, like whether a small control that hides some detail is now open or closed. I feel things that are used only locally should be stored only locally, like in useState.
Often the number of things left is quite small, and putting them in one or a few Contexts is fine, except if your application becomes quite complicated.
But, Redux comes with its own advantages -- a single way to make undo functionality, a way to serialize / rehydrate its entire state, and Redux dev tools that allow looking at the action history in case you find yourself debugging complicated effects to do with the order in which happened. If you use this heavily, then you would be inclined to store more state in Redux than you would if you only make a little use of these advantages.
So it's matter of degree, it's more art than exact science, there are no strict rules. "Put everything in Redux" certainly sounds suspect to me, but who knows about your team.
If your state and operations on that state are moderate in size then react Context API is really smart enough to support you. Even, #danAbrvmov writes:
React Redux uses context internally but it doesn’t expose this fact in the public API. So you should feel much safer using context via React Redux than directly because if it changes, the burden of updating the code will be on React Redux and not you.
You may like reading his article: You Might Not Need Redux
As for, you see some companies and projects using Redux, this is because Redux is out there for a long time and Context API is newer. Moreover, if you really need some features like redux-thunk, you can still use it.
I doubt you clearly understand how the state is handled in React.
In a typical React application, data is passed top-down (parent to child) via props. You may like my answer on another post to learn when we may need Context API or Redux at all: https://stackoverflow.com/a/62980048/9857078
Pardon my ignorance. I am still pretty new to React. Is there anything particularly wrong with storing certain values in the state of the App component and passing a prop to child components that allows them to set the state of App? Of course I wouldn't use it to store all of the state for child components, just certain values I want available everywhere.
You can use React-context or Redux, for example, redux is a predictable state container for JavaScript apps (something like a global state, which could be accessed all over the project)
check it here https://redux.js.org/
I think you should look into redux/react-redux or recoil. These are libraries which are made to handle global state (or state which is needed in multiple places).
However if your app is very small and does not have much state it is imo fine to keep that state in the App component. Just make sure that you'll look for alternatives once you application grows as it isn't very performant or readbable to do so in bigger projects.
Redux was/is considered the go to state management library for react applications by many. It integrates great with react and is very mature. I would go for it if you expect your application to have a complex global state or become more and more complex over time. There are also great companion libraries available. For example redux-saga if you want to handle side effects or redux-persist if you want to persist you apps state.
Recoil is still pretty new and especially made for react apps. Even though it is only around for a few months you can probably expect it to develop nicely as it is backed and used by facebook. Arguably it is the more performant and easier to get into choice, but you'll probably find less guides and tutorials due to its novelty.
If you only have a few values you could also just use reacts context api.
You have two options, React-context or Redux, both of them works as you want
It is certainly right to do so in some cases, other options are using react context or react-redux
For a simple value your first option is ok, if you need to store more complicated values and need to update them frequently I'd suggest using any of the other options.
They both have some significant learning and setup curve though.
It depends how deep is your application tree. If it is a very simple app, you can get away with just using React state. If it is something more complex (like 3 or more levels deep), I suggest to use React Context (for simple values) or Redux for more complex actions.
I'm starting a new React app and, seeing all the news in the ecosystem, I want to go slow and actually consider my choices, starting with just React/Webpack/Babel, and introducing more.
The first of these choices is whether to use Flux or not (more precisely, Redux, which looks great and seems to have won the flux wars). Here is where I am:
I understand Redux's benefits, summarized on SO by Dan Abramov. They look great, but I'd rather introduce things one step at a time.
In plain React, parent→child communication is done with props, and child→parent communication happens with callbacks. See Doc / Communicate Between Components, or SO / Child to parent communication in React (JSX) without flux, or this codeacademy Redux tutorial which starts out by saying "no need for Redux if you're fine with plain React and all your data in a root component".
Which looks just fine for my purpose...
... however, the sad part is that these callbacks have to be passed down the component chain, which becomes quickly tedious as the levels of nesting grow.
To solve this without introducing new dependencies, I found two articles (1: Andrew Farmer, 2: Hao Chuan) encouraging usage of the recently-introduced context feature of React.
→ Using context would let me expose my model-mutating callbacks to my child components. To me it doesn't sound like a horrible misuse: I wouldn't be passing model data, just references to functions for binding on event handlers.
Does it sound sane?
Any other plain-React suggestion for convenient child→parent communication?
Thanks.
Answering my own question after watching Dan Abramov's Getting Started with Redux series, which I warmly recommend.
Yes it looks like it's sane: Redux faced the very same problem and solved it with Context (at least initially, the implementation may have changed). It is implemented and packaged (among other things) in the react-redux bindings under the <Provider> component and the connect() function.
Initially, at the start of step 24 - Passing the Store Down Explicitly via Props , we have a Todo app with a Redux store available as top-level variable. This sucks (for 1. testability/mockability, 2. server rendering needing "a different store instance for every request because different requests have different data"), so the store is demoted from top-level variable to a root component prop.
As in my case, having to pass the store as prop to each component is annoying, so in 25 - Passing the Store Down Implicitly via Context, Dan demonstrates using Context to pass the Redux store to arbitrarily nested components.
It is followed by 26 - Passing the Store Down with <Provider> from react-redux, explaining how this was encapsulated in the react-redux bindings.
And 27 - Generating Containers with connect() from React Redux further encapsulates generation of a container component from a presentational component.
Personally, I find the question quite simple to answer, if you think about the way dependency injection in Angular works. In Angular you have your DOM, and then you have all those services, providers, factories, constants and whatnot, which are independent of the DOM structure and can be imported simply by mentioning their name when creating modules or controllers.
I liken the use of this.context to DI. The difference w.r.t to Angular is that instead of stating the dependencies using function parameter names, you use childContextTypes and instead of getting the dependencies as function arguments, you get them through this.context.
In this sense, asking the question whether passing model mutators through this.context is sane, boils down to whether it makes sense in Angular to register your model for dependency injection. I've never seen a problem with the latter, therefore I deduce that the former is also quite OK.
I'm not saying that it suits the spirit of the library, though. Dependency injection and in particular managing dependencies between injected component is not as explicit, so one may argue that it's not the React way. I leave this philosophical discussion to others.
I'm getting to be a fan of David Nolen's Om library.
I want to build a not-too-big web app in our team, but I cannot really convince my teammates to switch to ClojureScript.
Is there a way I can use the principles used in om but building the app in JavaScript?
I'm thinking something like:
immutable-js or mori for immutable data structures
js-csp for CSP
just a normal javascript object for the app-state atom
immutable-js for cursors
something for keeping track of the app-state and sending notification base on cursors
I'm struggling with number 5 above.
Has anybody ventured into this territory or has any suggestions? Maybe someone has tried building a react.js app using immutable-js?
Edit July 2015: currently the most promising framework based on immutability is Redux! take a look! It does not use cursors like Om (neither Om Next does not use cursors).
Cursors are not really scalable, despite using CQRS principles described below, it still creates too much boilerplate in components, that is hard to maintain, and add friction when you want to move components around in an existing app.
Also, it's not clear for many devs on when to use and not use cursors, and I see devs using cursors in place they should not be used, making the components less reusable that components taking simple props.
Redux uses connect(), and clearly explains when to use it (container components), and when not to (stateless/reusable components). It solves the boilerplate problem of passing down cursors down the tree, and performs greatly without too much compromises.
I've written about drawbacks of not using connect() here
Despite not using cursors anymore, most parts of my answer remains valid IMHO
I have done it myself in our startup internal framework atom-react
Some alternatives in JS are Morearty, React-cursors, Omniscient or Baobab
At that time there was no immutable-js yet and I didn't do the migration, still using plain JS objects (frozen).
I don't think using a persistent data structures lib is really required unless you have very large lists that you modify/copy often. You could use these projects when you notice performance problems as an optimization but it does not seem to be required to implement the Om's concepts to leverage shouldComponentUpdate. One thing that can be interesting is the part of immutable-js about batching mutations. But anyway I still think it's optimization and is not a core prerequisite to have very decent performances with React using Om's concepts.
You can find our opensource code here:
It has the concept of a Clojurescript Atom which is a swappable reference to an immutable object (frozen with DeepFreeze). It also has the concept of transaction, in case you want multiple parts of the state to be updated atomically. And you can listen to the Atom changes (end of transaction) to trigger the React rendering.
It has the concept of cursor, like in Om (like a functional lens). It permits for components to be able to render the state, but also modify it easily. This is handy for forms as you can link to cursors directly for 2-way data binding:
<input type="text" valueLink={this.linkCursor(myCursor)}/>
It has the concept of pure render, optimized out of the box, like in Om
Differences with Om:
No local state (this.setState(o) forbidden)
In Atom-React components, you can't have a local component state. All the state is stored outside of React. Unless you have integration needs of existing Js libraries (you can still use regular React classes), you store all the state in the Atom (even for async/loading values) and the whole app rerenders itself from the main React component. React is then just a templating engine, very efficient, that transform a JSON state into DOM. I find this very handy because I can log the current Atom state on every render, and then debugging the rendering code is so easy. Thanks to out of the box shouldComponentUpdate it is fast enough, that I can even rerender the full app whenever a user press a new keyboard key on a text input, or hover a button with a mouse. Even on a mobile phone!
Opinionated way to manage state (inspired by CQRS/EventSourcing and Flux)
Atom-React have a very opinionated way to manage the state inspired by Flux and CQRS. Once you have all your state outside of React, and you have an efficient way to transform that JSON state to DOM, you will find out that the remaining difficulty is to manage your JSON state.
Some of these difficulties encountered are:
How to handle asynchronous values
How to handle visual effects requiring DOM changes (mouse hover or focus for exemple)
How to organise your state so that it scales on a large team
Where to fire the ajax requests.
So I end up with the notion of Store, inspired by the Facebook Flux architecture.
The point is that I really dislike the fact that a Flux store can actually depend on another, requiring to orchestrate actions through a complex dispatcher. And you end up having to understand the state of multiple stores to be able to render them.
In Atom-React, the Store is just a "reserved namespace" inside the state hold by the Atom.
So I prefer all stores to be updated from an event stream of what happened in the application. Each store is independant, and does not access the data of other stores (exactly like in a CQRS architecture, where components receive exactly the same events, are hosted in different machines, and manage their own state like they want to). This makes it easier to maintain as when you are developping a new component you just have to understand only the state of one store. This somehow leads to data duplication because now multiple stores may have to keep the same data in some cases (for exemple, on a SPA, it is probable you want the current user id in many places of your app). But if 2 stores put the same object in their state (coming from an event) this actually does not consume any additional data as this is still 1 object, referenced twice in the 2 different stores.
To understand the reasons behind this choice, you can read blog posts of CQRS leader Udi Dahan,The Fallacy Of ReUse and others about Autonomous Components.
So, a store is just a piece of code that receive events and updates its namespaced state in the Atom.
This moves the complexity of state management to another layer. Now the hardest is to define with precision which are your application events.
Note that this project is still very unstable and undocumented/not well tested. But we already use it here with great success. If you want to discuss about it or contribute, you can reach me on IRC: Sebastien-L in #reactjs.
This is what it feels to develop a SPA with this framework. Everytime it is rendered, with debug mode, you have:
The time it took to transform the JSON to Virtual DOM and apply it to the real DOM.
The state logged to help you debug your app
Wasted time thanks to React.addons.Perf
A path diff compared to previous state to easily know what has changed
Check this screenshot:
Some advantages that this kind of framework can bring that I have not explored so much yet:
You really have undo/redo built in (this worked out of the box in my real production app, not just a TodoMVC). However IMHO most of actions in many apps are actually producing side effects on a server, so it does not always make sens to reverse the UI to a previous state, as the previous state would be stale
You can record state snapshots, and load them in another browser. CircleCI has shown this in action on this video
You can record "videos" of user sessions in JSON format, send them to your backend server for debug or replay the video. You can live stream a user session to another browser for user assistance (or spying to check live UX behavior of your users). Sending states can be quite expensive but probably formats like Avro can help. Or if your app event stream is serializable you can simply stream those events. I already implemented that easily in the framework and it works in my production app (just for fun, it does not transmit anything to the backend yet)
Time traveling debugging ca be made possible like in ELM
I've made a video of the "record user session in JSON" feature for those interested.
You can have Om like app state without yet another React wrapper and with pure Flux - check it here https://github.com/steida/este That's my very complete React starter kit.