Server side prop value undefined only in the component section - javascript

I have the following where I am able to print the data coming from getServerSideProps.
But when I pass it on to the component section, the prop value posts is undefined. Why?
The following is under /pages and is inside the base index.tsx file.
import type { NextPage } from 'next'
import Post from '../components/Post'
const Home: NextPage = ({ posts }) => {
// This prints undefined. This is the issue.
console.log(posts)
return (
<div>
<Post posts={posts}/>
</div>
)
}
export default Home
export const getServerSideProps = async () => {
const response = await fetch('http://localhost:8080/posts/all')
const data = await response.json()
// this prints correctly
console.log(data)
return {
props: {
posts: data
}
}
};
Updates to show _app.tsx file
import Home from '../pages';
const TestApp = () => {
return <>
<Home />
</>
}
export default TestApp

Remove the custom _app.tsx file or update it to accept a Component prop and render it as shown in the Nextjs documentation for a Custom App.
The problem is this custom App is always rendering the Home component (with no props) so it's printing undefined. Then, try navigating to / on localhost. It should render the index.tsx file and properly invoke getServerSideProps and pass the result to the component as you expect.

Related

How to use SSR data fetching in nextjs with apollo client?

I am try to use apollo-client with nextjs. Here I want to fetch data in getServerSideProps. Suppose I have 2 components and one page-
section.tsx this is component-1
const Section = () => {
return (
<div>
Section
</div>
);
};
export default Section;
mobile.tsx this is component 2
const Mobile = () => {
return (
<div>
Mobile
</div>
);
};
export default Mobile;
Now I call this two component into home page.
index.tsx-
const Home: NextPage = () => {
return (
<Container disableGutters maxWidth="xxl">
<Section />
<Mobile />
</Container>
);
};
export default Home;
export const getServerSideProps: GetServerSideProps = async () => {
const { data } = await client.query({ query: GET_USER_LIST })
return { props: {} }
}
Here you can see that in getServerSideProps I already fetch my data.
My question is How can I directly access this data form Section component and Mobile component without passing props. I don't want to pass props, because if my component tree will be more longer, then it will be difficult to manage props.
From appollo docs, I alreay know that apollo client do the same with redux state manager. So please tell me how can I access this data from any component that already fetched in getServerSideProps. Is it possible?. If not then how can what is the solutions.
How about using context api if you want to avoid prop drilling? By putting data into context, you can access it from any child component. Get the data from the SSR and put it into the context.
Below is the example
import React, {createContext, useContext} from "react";
export default function Home({data}) {
return <DataContext.Provider value={{data}}>
<div>
<Section/>
<Mobile/>
</div>
</DataContext.Provider>
}
export async function getServerSideProps() {
const data = 'hello world' //Get from api
return {
props: {data},
}
}
function Section() {
return <div>
Section
</div>
}
function Mobile() {
const context = useContext(DataContext);
return <div>
Mobile {context.data}
</div>
}
const DataContext = createContext({});
Now, as long as your tree structure grows within the DataContext provider, each child node will have access to data in the context.
Hope this helps.

How to make a basic external data fetch using Next.js and import component into another

I have the code below in pages/github and when I go to localhost:3000/github the code executes as expected. I get JSON data.
function GithubAPI(props) {
// Render posts...
return (<div>{props.data.name}</div>)
}
// This function gets called at build time
export async function getStaticProps() {
// Call an external API endpoint to get posts
const res = await fetch('https://api.github.com/repos/vercel/next.js')
const data= await res.json()
console.log(data)
return {
props: {
data,
},
}
}
export default GithubAPI
When I import this component into another component I get problems.
pages/about
import GithubAPI from './github'
function About(props) {
console.log(props)
return (
<div>
<div>About</div>
<GithubAPI/> {/* TypeError: Cannot read property 'name' of undefined */}
</div>
)
}
export default About
I do not know how the developers of Next.js expect us to structure our code so that we can make these kinds of API calls and still export our components for import into other components. How am I expected to do this?
You cannot run getStaticProps/getServerSideProps in any non-page components. One must prop pass instead.

Using redux in NEXT.JS

In my application on Next.Js i use redux and redux saga. I want to use ssr making http requests:
export const getStaticProps = wrapper.getStaticProps(async ({ store }) => {
store.dispatch(getDataRequest());
store.dispatch(END);
await store.sagaTask.toPromise();
});
In the same time i want to get data of the above result:
const selector = useSelector((s) => s);
console.log(selector);
The issue is that, when i run the application i get an error:
Error: could not find react-redux context value; please ensure the component is wrapped in a <Provider>
I used the provider but the data doesn't appear. Question: How to solve the issue in my application?
demo: https://codesandbox.io/s/awesome-butterfly-f7vgd?file=/pages/store/saga.js
this is your _app component:
function App({ Component, pageProps }) {
return (
<div>
<Provider store={makeStore}>
<Component {...pageProps} />
</Provider>
</div>
);
}
you dont need to wrap it with Provider. this is the only thing you need to do in _app.
export default wrapper.withRedux(App)
this is getStatisProps in your pages/index.js
export const getStaticProps = wrapper.getStaticProps(async ({ store }) => {
store.dispatch(getDataRequest());
store.dispatch(END);
await store.sagaTask.toPromise();
});
see store is already passed here. You will be accesing state via store.getState(). this is how it should be
export const getStaticProps = wrapper.getStaticProps(async ({ store }) => {
store.dispatch(getDataRequest());
store.dispatch(END);
await store.sagaTask.toPromise();
const state = store.getState();
return {props:{data:state}} // since you have only one reducer
});
now data will be passed as a prop to your component. if you console.log(props.data) inside the component, you should be seeing your dataReducer

Data from Gatsby GraphQL always returns undefined?

Gatsby noob here so please bear with me. I have a component that accepts props from the index.js where it is supposed to receive data from an array of objects but will always receive the error TypeError: Cannot read property 'map' of undefined where it's referring to the Hero.js component index.js is calling for.
My assumption is that the data being queried in index.js is either not specific enough or that it is rendering the component before data is received. Here is the index.js file:
import { graphql } from 'gatsby';
import { Layout, SEO, Hero } from 'components';
const IndexPage = ({ data }) => {
const dataFetch = data.contentfulTemplateIndex.heroes;
let tester = () => {
for (let count = 0; count < dataFetch.length; count++) {
return <Hero {...props} />;
}
};
console.log(dataFetch);
let props = {
impactText: dataFetch.impactText,
labels: dataFetch.labels,
primaryLabel: dataFetch.primaryLabel,
location: dataFetch.location
// supportingText: dataFetch.supportingText.json
};
return (
<Layout>
{dataFetch && tester()}
</Layout>
);
};
export const query = graphql`
query {
contentfulTemplateIndex {
heroes {
image {
fluid {
src
}
}
impactText
labels
location
primaryLabel
supportingText {
json
}
}
}
}
`;
export default IndexPage;
Here is the Hero.js component which index.js is calling:
import { Link } from 'gatsby';
import { documentToReactComponents } from '#contentful/rich-text-react-renderer';
import cx from 'classnames';
import styles from './hero.module.scss';
const Hero = (props) => {
return (
<div>
<ul>
<Link className={styles.pills}>{props.primaryLabel}</Link>
{props.labels.map((label) => {
return <Link className={styles.pills}>{label}</Link>;
})}
</ul>
<div className={styles.grid}>
<h1>{props.impactText}</h1>
</div>
</div>
);
};
export default Hero;
It's impossible for an outsider to debug your code without a minimum reproducable example.
The best way to debug GraphQL is to use the GraphiQL interface of your browser.
Run gatsby develop. If it fails because of the TypeError remove the lines of code that cause the type error (but not the code of your GraphQL query!). You need to get your development server runnning.
Open your browser, use the URL: http://localhost:8000/___graphql
Copy your graphQL query from your code and paste it into the GraphiQL query window.
Can you access your data there? If not you made a mistake writing your query or the data is not where it's supposed to be.
This way you can make sure the data exists.
It also helps to console.log(props) so you can examine the data object:
const Hero = (props) => {
console.log(props);
return (

Next.js - understanding getInitialProps

I have an app that uses next.js along with Apollo/ Graphql and i'm trying to fully understand how the getInitialProps lifecycle hook works.
The lifecycle getInitialProps in my understanding is used to set some initial props that will render server side for when the app first loads which can be used prefetch data from a database in order to help SEO or simply to enhance page load time.
My question is this:
Every time I have a query component that fetches some data in my
components across my app, do I have to use getInitialProps to be
sure that data will be rendered server side?
My understanding is also that getInitialProps will only work in the page index components (as well as in _app.js), this would mean that any component lower down in the component tree would not have access to this lifecycle and would need to get some initial props from way up at the page level and then have them passed down the component tree. (would be great if someone could confirm this assumption)
Here is my code:
_app.js (in /pages folder)
import App, { Container } from 'next/app';
import { ApolloProvider } from 'react-apollo';
class AppComponent extends App {
static async getInitialProps({ Component, ctx }) {
let pageProps = {};
if (Component.getInitialProps) {
pageProps = await Component.getInitialProps(ctx)
}
// this exposes the query to the user
pageProps.query = ctx.query;
return { pageProps };
}
render() {
const { Component, apollo, pageProps } = this.props;
return (
<Container>
<ApolloProvider client={apollo}>
<Component client={client} {...pageProps} />
</ApolloProvider>
</Container>
);
}
}
export default AppComponent;
Index.js (in /pages/users folder)
import React, { PureComponent } from 'react';
import { Query } from 'react-apollo';
import gql from 'graphql-tag';
const USERS_QUERY = gql`
query USERS_QUERY {
users {
id
firstName
}
}
`;
class Index extends PureComponent {
render() {
return (
<Query query={USERS_QUERY}>
{({data}) => {
return data.map(user => <div>{user.firstName}</div>);
}}
</Query>
);
}
}
export default Index;
The answer is NO
If you use Apollo with Next JS you will not have to use getInitialProps on each page to get some initial data rendered server side. The following configuration for getInitialProps is enough for all the components to render out with their respective queries if they have <Query> components in them
static async getInitialProps({ Component, ctx }) {
let pageProps = {};
if (Component.getInitialProps) {
pageProps = await Component.getInitialProps(ctx)
}
// this exposes the query to the user
pageProps.query = ctx.query;
return { pageProps };
}
My issue and why I wasnt seeing any server side rendering is that Heroku or Now wouldnt perform SSR with a public URL ie my-app.heroku.com. To resolve this I purchased and applied a custom URL in Heroku and it worked. Along with a custom URL I had the following configuration in my Apollo config
const request = (operation) => {
operation.setContext({
fetchOptions: {
credentials: 'include'
},
headers: { cookie: headers.cookie }
});
};
This completely resolved it and now I have SSR without the pain of having to manually set getInitialProps on each page
Hope this helps someone

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