How does the React Context API work under the hood? - reactjs

So far I can only find descriptions of how to use the Context API, but not how it works, especially how consumer components are triggered to re-render. Links to source code would be awesome!

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About calling API in reactjs

I have a question about calling API in react.
Example in the website. We have a lot of page. Each page has a lot of components. And each component has its own data need to get in server.
I see we have two way to call API is:
First. We call all API of each page in a root of each page then set the data to state. After that, we pass data to children Component.
Second. In each component, we call its API to get its data then set the data to component 's state.
So which is better. I need an explain about that.
Thanks you,
There are many ways to pass Data through out the components.
If the application is small and there are small number of child components you can go by making calls in Root folder.
There would be some components that always doesn't render and only rendered based on specific conditions at this point you can go by making calls from that component.
Using redux and redux thunk is always an option if the data is needed in many components and data can be accessed at any point of time.
As noted in the previous answers/comments you could do either one of these. If you plan to use redux it might be easier to chain the api calls in a single action w/ thunk that gets ran on main component load.
Context or Redux would do you well so you don't have to pass tons of data through prop levels.(prop drilling)
I would suggest Redux, IMO context gets too cluttered and by the time you've properly atomized your code to clean up everything you may as well have just went through the overhead of adding redux.
What you should ask yourself is-
Does it make sense to have all this data load at the same time?
Is it appropriate for some api calls to be made from the components that will use them?
You have creative license to do what works best for you.

React data flow

I am trying to create a blog application and I am a bit confused on the data flow patterns of React.
Should I be trying to use something like Redux to store all of my posts after fetching the posts? Do I use local storage?
How do I then tell a component to render the 'expanded' version of the post? Is it better to re-use a 'post' component or should I just create two seperate components, one for the title and one for the full post?
I know it's two questions in one, but they kind of go together. Thanks in advance
Here's what I've found out about these topics after 6 months into my self-taught React journey.
In my opinion, React built-in features are more than enough to handle state for a small to medium applications (especially if you're working alone as a single developer).
If you turn to Redux right away, you'll have to learn this whole new pattern of handling state in a single immutable store and how to connect your components to it.
Since you will be most likely fetching data asynchronously, you'll need a helper library to work async on Redux: redux-thunk or redux-saga.
So right from the start, you'll have to add:
redux
react-redux
redux-thunk OR redux-saga
That is a lot of documentation to digest. It's perfectly doable, but I couldn't agree more with this quote:
don't solve problems that you don't have
It will be hard to learn those tools, since you've never faced the problems that they solve. Problems that you don't encounter just yet when you're starting to learn React.
Read this (from Redux creator):
https://medium.com/#dan_abramov/you-might-not-need-redux-be46360cf367
So, my recommendation to you:
Learn basic React (with classes):
https://reactjs.org/docs/getting-started.html
Then learn React Hooks (and you can basically forget about class components):
https://reactjs.org/docs/hooks-intro.html
Build your project using only React at first. And see how it goes. Then you can read more about Redux and what it does, and will be able to make a better choice on if you really need it or not.
From what you've told us about your project:
Keep a state for all your posts in a component high in the tree. Maybe inside the <App/> component itself.
Build your functions to fetch and update post data and update the state with the response.
Render how many components as you wish. Displaying full info about the post inside a BlogPostComponent or simplified version inside a BlogPostThumbnailCard with just the thumbnail and the title, for example.
If you want to be ready for the next versions of React and have a shorter code, you should try the hooks and avoid Classes
https://reactjs.org/docs/hooks-intro.html
You can organize your code as you want, but this is more interesting to have scalability with your components and reuse them with different properties

How to implement React-navigation with Redux?

I've just setup my Redux store in React native app.
I moved to initialize React navigation for my project, i though that, as long as i'm using Redux to manage my app state, then the default option is that redux also is taking care of Navigation, and it should be hooked up to Redux, i opened React navigation docs, it says literally:
"Think twice before you consider doing this, there is an incredibly good chance that you do not need to do t his!"
So, is it a good practice to manage navigation with Redux, or just implement basic navigation the normal way (outside Redux) ?
Thanks in advance.
React Navigation manages its own state internally (using its own redux store I think...). There's no real need to connect react-navigation state to your own app's redux store since they expose API to do everything you might need to even without the navigation prop. Also it looks like they're dropping support for redux integration in the next version so beware of deprecation.
This is one of those cases where people may introduce unnecessary complexity and research into the project just to be happy about how "neat" the code runs even when it doesn't offer any real deliverable.

Apollo client for store in React app - best practises?

I feel the hardest part going the Apollo/GraphQl pathway is deciding patterns rather than learning the syntax.
Having moved all app store from Redux to Apollo cache I am a few days later still struggling with a best way to have components communicate and commonly access the Apollo store.
I could write pages about different implementations but the questions remains as I haven't found any articles or code examples and the forums are dead silent about this - how are others doing this?
To add some to the discussion I have only one React state in top-level (parent) component:
{dispatch: (...dispatch function...), actionType, actionPayload}
and distribute these through by props and React Context to child components deep down the tree. Parent then monitors dispatched functions and handles most of them (like data manipulations) and passes unhandled actions down the tree. It feels much like Redux but the store is 100% in Apollo.
This has been a thready path and I feel my current pattern will likely change a lot so I'd love to hear from others. Components communicating and app store are the core of every app, surely there must be others out there?!

What is the use of Redux-Router in addition to reac-router?

guys. When I go through the documentation of redux-router, I just cannot understand why do we need it?
Here is what the documentation is trying to explain:
React Router is a fantastic routing library, but one downside is that
it abstracts away a very crucial piece of application state — the
current route! This abstraction is super useful for route matching and
rendering, but the API for interacting with the router to 1) trigger
transitions and 2) react to state changes within the component
lifecycle leaves something to be desired.
It turns out we already solved these problems with Flux (and Redux):
We use action creators to trigger state changes, and we use
higher-order components to subscribe to state changes.
This library allows you to keep your router state inside your Redux
store. So getting the current pathname, query, and params is as easy
as selecting any other part of your application state.
As far as I can understand, it is trying to say redux router can keep router state inside redux store so that we can get route info more conveniently.
But within react-router, I can also easily do it.
Like path="messages/:id", I can use this.props.params.id to get the params.
Can someone explain in what scenario redux-router bring its benefit?
Redux (and in general, the flux pattern) is all about having the entire application state stored in one central place. This has the benefit of easier debugging and makes it easier to implement certain features.
If you've ever used the redux-devtools in a react app with react-router, you'll notice that its only of limited use, because you can't replay the entire lifecycle of the application. When the user changes routes, that's not recorded in the redux store. Redux Router keeps the route state in the store.
You could use this for debugging, you could serialise the entire store history and log it elsewhere to replay user sessions. You could hook into it to implement full undo, or log analytics events.
redux-simple-router is a library which could help you understand how to use react router in a redux application.
It is a very simple library stores the URL in redux state and keeps it in sync with any react-router changes.
redux-simple-router compared to redux-router is:
Much smaller and simpler. You don't need to learn another library on top of everything else.
Encourages direct access of react-router APIs. Need server-side rendering, or something else advanced? Just read react-router's docs.
Only stores the current URL and state, whereas redux-router stores the entire location object from react-router.
Follow one of the these 2 examples to get up and running:
redux-simple-router-example
redux-frontend-boilerplate

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