Not sure if it's the right website to ask this question but I I'll give it a go.
When building a web app with React and Redux, how should one use the connect() function? Is the goal to only have one container connected to the store at the top that passes the props to it's children or to have multiple containers connected to the store that passes down props to their children?
I've built a small web app that only has one container that is connected to the store and therefore it passes all its props down.
I was wondering what solution was best and if it's the multiple containers connected one, how does one build his app's architecture that way?
Thank you.
Quoting the Redux FAQ at http://redux.js.org/docs/faq/ReactRedux.html#react-multiple-components :
Early Redux documentation advised that you should only have a few connected components near the top of your component tree. However, time and experience has shown that that generally requires a few components to know too much about the data requirements of all their descendants, and forces them to pass down a confusing number of props.
The current suggested best practice is to categorize your components as “presentational” or “container” components, and extract a connected container component wherever it makes sense:
Emphasizing “one container component at the top” in Redux examples was a mistake. Don't take this as a maxim. Try to keep your presentation components separate. Create container components by connecting them when it's convenient. Whenever you feel like you're duplicating code in parent components to provide data for same kinds of children, time to extract a container. Generally as soon as you feel a parent knows too much about “personal” data or actions of its children, time to extract a container.
In fact, benchmarks have shown that more connected components generally leads to better performance than fewer connected components.
In general, try to find a balance between understandable data flow and areas of responsibility with your components.
Related
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
I am trying to understand what is redux in reactjs but it is not clear for me.react working even without redux then what is the use of redux in reactjs
Redux helps you manage the states across your application much more effectively by accessing them in a commonly accessible space (a store) by all of your components.
Imagine if you had an application which had children components nested 5 or 6 layers deep, you wouldn't want to bind the state each time and pass it all the way down. Let's say each of those nested components relied on the state change, and needed a way to alter the shared state. It would be really tedious to have to bind the state and a method of accessing the state all the way down the chain. Enter redux - much easier to access and manage states.
Another side effect you'll run into as your application grows are unintended side-effects. Neither of these issues are completely eliminated by redux - but it's intended to organize code better, and in turn make it easier to debug.
If you haven't hit the limitations React has out of the box - there is no need to grab for a new tool, Redux, or otherwise. BUT here is a built-in Redux alternative native to React:
https://reactjs.org/docs/context.html
I am trying redux right now and very excited about ideas behind it, but first real task ruined the whole thing.
In Redux we should store immutable state and produce some reducers to transform it. It means that every state could be reproduced by given previous state and a list of actions fired.
But what if I need to store third-party/legacy stateful object? For example it may be something like gallery or websocket client.
I assume that I'm able to use reducers to start/stop/manage it somehow, but the state I have no longer stateless and it not guaranteed to be repeatable with given list of reducers (websocket client may generate new session id or even be unable to maintain connection).
What is convenient way to solve these issues?
As I see this, your problem boils down to: How do you mix Redux with stateful components (legacy/third party)?
You are right, Redux is better suited for controlled components, that is, components that are mostly stateless and are supposed to receive everything as props. Just keep in mind that having some state doesn't necessarily make the component unusable in Redux. Example: For an Autocomplete component, the "open" state (whether or not the dropdown is visible) doesn't necessarily has to be controlled by Redux. So, depending on the how the component is implemented, you're definitely having a hard time integrating it into Redux, or maybe not.
You have 2 options: You either refactor the problematic components so they're now controlled, or you don't keep their state on Redux (you're not required to). The answer will vary depending on the circumstances. There's not a globally accepted solution for your case, that I know of.
Here's a nice explanation from the FAQ docs. In short:
Do I have to put all my state into Redux? Should I ever use React's setState()?
There is no “right” answer for this. Some users prefer to keep every single piece of data in Redux, to maintain a fully serializable and controlled version of their application at all times. Others prefer to keep non-critical or UI state, such as “is this dropdown currently open”, inside a component's internal state.
Using local component state is fine. As a developer, it is your job to determine what kinds of state make up your application, and where each piece of state should live. Find a balance that works for you, and go with it.
There's a bunch more info there -- worth reading the whole thing.
Remember: There is no magic to redux; it's just a wrapper/container that is setting the props for you.
You can even use shouldComponentUpdate to manage how changing your stateful component's props should trigger the rendering.
Or leverging on connect's
areStatesEqual
areStatePropsEqual
areOwnPropsEqual
areMergedPropsEqual
for greater control
related: https://stackoverflow.com/questions/58027300/what-is-the-main-difference-between-using-react-redux-hooks-and-react-redux-conn#:~:text=connect%20can%20be%20used%20with,used%20with%20function%20components%20only.&text=Using%20hooks%20is%20simpler.,disposal%20in%20comparison%20with%20connect%20.
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 was wondering, how much state does really belong into the stores, and not into the components? I've read at some places that really all state should live inside the stores.
Would that include really component specific stuff, like input values (before submitting), input validation, if a modal is open, if something has been clicked etc?
What are the best practices here?
The obvious answer:
Keep component specific state (input value, modal open/ closed, stuff clicked, layout, formatting) inside the component state as much as possible.
And app specific state inside the store. Which includes, but is not limited to, stuff you send back and forth with a server.
That said, there is a lot of grey area here:
are filters applied to a search list component state? Or app state (if you save filters for future visits to the same page)?
are visited links in a global root-menu root-component state or app state?
if you are using optimistic updates, you may have a need to save user input stuff in the store, before and after communication with the server.
Some rules of thumb I use:
State belongs in component if it has the same lifecycle as the component (so if the state does not need to exist before the component mounts, and if it can be forgotten after the component unmounts)
If the state needs to be remembered when closing and reopening app, it is probably best put inside the store (where you do exchanges with server and/or localstorage)
If in doubt, start with state in component only: it keeps state much more localised (to the component) and keeps your code more manageable. At a later stage, you can always move the state to the store.
Keeping everything in flux stores may be benefitial for some apps.
So first, you should try to decide whether your app is like this.
If you're not sure whether a piece of state belongs to a flux store, then it's most likely that it doesn't.
You'll know when you need flux. And when you reach that level of understanding of whether such application architecture is appropriate for you, you'll probably know the answer to your initial question as well.
But of course it's nice to have some kind of specific guide, maybe just a mental guide, telling you when to keep state inside the component and when not to.
I'd go with these guides:
Is this state purely UI-related? Then you probably don't need to keep it in the store.
Is this state shared anywhere else outside the component? If not, then don't put it in the store. It's fine inside the component.
Can this state be persisted in the URL? If so, then don't put it in the store; put it in the url! It might be a search query of an input or a currently opened tab.
There may be exceptions to all of these, but in general I believe this to correspond well to the original ideas of a flux app.
P.S. Also I should say that there are a lot of talks saying that you should (may) keep all your UI inside an immutable state tree. That's how redux is introduced to lots of people. I think you should understand that while this is a great concept and it allows you so save/replay any user interactions, it is more often than not unnecessary and it's not what the main idea of Flux is about. And redux itself is a great flux tool that doesn't force you to keep all of the UI state in the stores.
View state specific to a component belongs in that component. App state which concerns many components belongs in a store.
It's debatable.
For example redux propose a pattern where ALL state belong in the store. Personally I think it is kind of impractical in many situations. It is very rare when I have any reason to store for example state of the button in the store.
But sometimes it can be advantageous. It is definitely easier to test when your whole app is stateless.