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Fetch only one element from Graphql in Gatsby

am new to gatsby and graphql and I came across a tutorial where it is mentioned to fetch all the data using .map. But I want to fetch only one element from the DB. So how do I do it?
import React from "react";
import Layout from "../components/layout";
import { useStaticQuery, graphql, Link } from "gatsby";
const Blogs = () => {
const data = useStaticQuery(
graphql`
query {
allMarkdownRemark(sort: { frontmatter: { date: ASC } }) {
edges {
node {
frontmatter {
title
date(formatString: "DD MM, YYYY")
}
excerpt
id
fields {
slug
}
}
}
}
}
`
);
return (
<Layout>
<ul>
{data.allMarkdownRemark.edges.map((edge) => {
return (
<li key={edge.node.id}>
<h2>
<Link to={`/blog/${edge.node.fields.slug}/`}>
{edge.node.frontmatter.title}
</Link>
</h2>
<div>
<span>
Posted on {edge.node.frontmatter.date}
</span>
</div>
<p>{edge.node.excerpt}</p>
<div>
<Link to={`/blog/${edge.node.fields.slug}/`}>Read More</Link>
</div>
</li>
);
})}
</ul>
</Layout>
);
};
export default Blogs;
Lets say I have multiple blogs and I wish to show only a specific one in a page through query like...
query MyQuery {
markdownRemark((id: {eq: "9ac19d6d"}) //Some ID {
title
description
content
}
}
How to get this on a page to display?
Thanks in advance!

Depending on what do you want to achieve:
If you want just a specific single post. You can filter your useStaticQuery to add the value of the id (if you know it beforehand) like:
query MyQuery {
markdownRemark((id: {eq: "123"}) {
title
description
content
}
}
useStaticQuery as the name points out, is static and doesn't accept dynamic values.
Another alternative is to get a specific position from data.allMarkdownRemark to display it.
If you just want a single post without any filter you can take advantage of the GraphQL query options:
{
allMarkdownRemark(limit: 1) {
edges {
node {
frontmatter {
title
}
}
}
}
}
If you are trying to create dynamic posts, hence each post template will display a different blog post (one per template), you need to pass a filter value from gatsby-node.js (where you create the post pages) to the template through Gatsby's context:
// gatsby-node.js
posts.forEach(({ node }, index) => {
createPage({
path: node.fields.slug,
component: path.resolve(`./src/templates/blog-post.js`),
context: {
id: node.id,
title: node.title
},
})
})
Note: here I'm lifting the id and the title. Use whatever works better for you
Now, you can take advantage of the context in your Blogs component (as long as it's a template):
const Blogs = ({data}) => {
console.log("your blog post is:", data)
return (
<Layout>
<h1>{data.markdownRemark.title}</h1>
</Layout>
);
};
export const query = graphql`
query($id: String!, $title: String!) {
markdownRemark((id: {eq: $id}) {
title
description
content
}
}
`
export default Blogs;
In other words: the first approach uses a static query (via useStaticQuery hook. Static, no dynamic parameters allowed) and the second uses a page query (only available in pages or templates)

With your query:
query MyQuery {
markdownRemark((id: {eq: "9ac19d6d"}) //Some ID {
title
description
content
}
}
Your data will be in data.markdownRemark
You can access those 3 fields directly.
const { title, description, content ] = data.markdownRemark;
return (
<Layout>
<div>
<p>{title}</p>
<p>{description]</p>
<p>{content}</p>
</div>
</Layout>
)

How to return a component/component-tag dynamically in vue/nuxt?

I am trying to convert a next.js app(https://medium.com/strapi/how-to-create-pages-on-the-fly-with-dynamic-zone-8eebe64a2e1) to a nuxt.js app. In this app I can fetch data from an API and the next.js app uses the APIs data to generate new pages with its corresponding content. Works well in Next.js.
The data/content from the API consists of Seo data for the page, some static values and very important of blocks. These blocks have an attribute called __component where the components name is saved and also have the components data like images, text, etc. So I only have to deal with next.js when adding new components.
In next.js I used the catch-all-route ./pages/[[...slug]].js to catch any slug an user may enter. Then the API is fired with the slug from the context.query and I get back the pages data if it exists. Now the APIs json data only needs to be passed to the blockmanager component.
const Universals = ({blocks}) => {
return <div><BlockManager blocks={blocks}></BlockManager></div>;
};
Here the blockmanager gets the json list of blocks, from which to parse the components.
import Hero from '../../blocks/Hero';
import Pricing from '../../blocks/Pricing';
const getBlockComponent = ({__component, ...rest}, index) => {
let Block;
switch (__component) {
case 'blocks.hero':
Block = Hero;
break;
case "blocks.prices":
Block = Pricing;
break;
}
return Block ? <Block key={`index-${index}`} {...rest}/> : null;
};
const BlockManager = ({ blocks }) => {
return <div> {blocks.map(getBlockComponent)} </div>;
};
BlockManager.defaultProps = {
blocks: [],
};
export default BlockManager;
How can I replicate this line now in nuxt js?
return Block ? <Block key={`index-${index}`} {...rest}/> : null;
How to return a component/component-tag dynamically in vue/nuxt ?
Is there maybe another solution to automatically insert the wanted component?
Maybe someones knows ho to convert the blockmanagers logic to vue/nuxt logic entirely.

I think you're looking for the is attribute. You can read about it here.
Your template would look like:
<component
:is="__component"
key={`index-${index}`}
/>

Ok I think I got it. No strange stuff actually. I thought about it too complicated. Wanted all dynamically created but no need as I saw later ...
<template v-if="blocks">
<div id="example-1">
<div v-for="({__component, ...rest}=block, i) in blocks" :key="i">
<Hero :data="rest" v-if="__component === 'blocks.hero'"/>
<Pricing :data="rest" v-if="__component === 'blocks.pricing'"/>
</div>
</div>
</template>
<script>
import Hero from '../../blocks/Hero/Hero.vue';
import Pricing from '../../blocks/Pricing/Pricing.vue';
export default {
components: {
Hero, Pricing
},
props: {
blocks: Array
}
}
</script>

React child component receives object. Why there is no visual update upon change of just one attribute of the object?

I have a Javascript complex data structure with 2 person fields - customer and payer (both are of type Person)
{
invoice: {
id: 123,
warehouseId: 456;
customer: {
id: 777,
name: "Coco"
}
payer: {
id: 778,
name: "Roro"
}
}
}
I am using child component for displaying Person object:
class ConnectedPersonFieldSet extends Component {
render () {
return
<div>
<div>{this.props.label}</div>
<div>{this.props.data.id}</div>
<div>{this.props.data.name}</div>
</div>
}
}
const PersonFieldSet = connect(mapStateToProps, mapDispatchToProps)(ConnectedPersonFieldSet);
export default PersonFieldSet;
And I have parent component that display full Invoice object and which has 2 child components for customer and payer respectively:
class ConnectedInvoice extends Component {
render () {
return
<div>
<div>{this.props.invoice.id}</div>
<div>{this.props.invoice.warehouseId}</div>
<PersonFieldSet label={"Customer" + /* this.props.customer.name */ } data={this.props.customer}></PersonFieldSet>
<PersonFieldSet label="Payer" data={this.props.payer}></PersonFieldSet>
</div>
}
}
const Invoice = connect(mapStateToProps, mapDispatchToProps)(ConnectedInvoice);
export default Invoice;
I have also complex logic that changes just invoice.customer.name. The updated customer name becomes visible in the Invoice component:
<div>{this.props.invoice.id}</div>
But, unfortunately, the
<PersonFieldSet label={"Customer" + /* this.props.customer.name */ } data={this.props.customer}></PersonFieldSet>
stays the same. If I uncomment /* this.props.customer.name */ then the updated customer.name becomes visible both in the label and in the name subcomponent of the PersonFieldSet.
So - my question is - why the child component, which receives the object, can not detect the change of the one attribute of this object and hence, does not update visual data upon the change of the one attribute of the object?
If the child component is able to feel somehow (e.g. via label={"..." + this.props.customer.name}) that the update of the attribute happened, then the child component displays the full update of all the attributes.
How to press the child component to detect that attributes can change the forwarded object?
I have read (e.g. React: why child component doesn't update when prop changes) that there is a trick with (more or less redundant) key attribute of the child element, but is this really my case?
My understanding is that React should support the hierarchical composition of both visual components and data components and do it without tricks or any other intrigues, but how to handle my situation? Should I really start to use hacks (key or others) in this situation that is pretty standard?
Added:
I am using Redux architecture for making updates - currently I am testing update of just one field - name:
const rootReducer = (state = initialState, action) => {
switch(action.type) {
case UPDATE_INVOICE_CUSTOMER: {
let person_id = action.payload.person_id;
let data = {
invoice: state.invoice
}
let newData = updateInvoiceByCustomer(data, person_id);
return {...state,
invoice: newData.invoice,
}
}
}
}
export function updateInvoiceByCustomer(data, person_id) {
let newData = {
invoice: data.invoice,
}
/* This will be replaced by the complex business logic, that retrieves
customer from the database using person_id and afterwards complex
calculations are done on the invoice, e.g. discounts and taxes
are assigned according to the rules relevant for the specific
customer. Possible all this code will have to be moved to the chain
of promises */
newData.invoice.customer.name='Test';
return newData;
}

Thanks #Yoshi for comments on my question and for persisting to check my Redux update logic. Indeed, when I have removed all the copying-update logic (which should be corrected to use cloning) and replaced it by:
return {
...state,
['invoice']: {...state['invoice'],
['customer']: {...state['invoice']['customer'],
['name']: 'REAL-TEST',
}
}
}
Then child component started to re-render and to show the actual value without any hacks or use of key-attributes. So, that was the cause of error.

Dynamically rendered images in Gatsby

I'm working on the blog based on React, TS and Gatsby.
Blog posts are based on markdown. Each blog post will have a similar header with title, time necessary to read the article and the logos of the technologies that the particular blog post will be about.
I have a problem with rendering those images dynamically. My idea was to create something like this in markdown
---
path: "/fourth"
date: "2021-06-02"
title: "TypeScript - intro"
readTime: "140"
author: "Adam Kniec"
imgs: [typescript, react]
---
That's the fourth blog post
after that I wanted to create a graphql query and get the imgs names like so:
export const postQuery = graphql`
query BlogPostByPath($path: String!) {
markdownRemark(frontmatter: { path: { eq: $path } }) {
html
frontmatter {
path
readTime
title
author
imgs
date
}
}
}
`;
I have the array of images in the props now and I wanted to render those images like this
{data.markdownRemark.frontmatter.imgs.map((imgPath) => {
const imgPatha = `../images/${imgPath}`;
return <StaticImage src={imgPatha} alt="asdasd" />;
})}
Unfortunately, gatsby gives me the warning
react_devtools_backend.js:2560 Image not loaded ../images/typescript
Is this the correct approach ? Please let me know what I'm doing wrong or how to render those images dynamically.

As it has been said by #coreyward you can't use dynamic props in the StaticImage component, it's a known restriction.
That said, you have two choices:
Using the standard img HTML tag.
Using the GatsbyImage component. To do it, you'll need to add the images in your filesystem to allow Gatsby to create the proper nodes and then, you will need to query them in your pages/templates. Without further details on the implementation, it's impossible to guess how your code should look like but the idea relies on something like:
import { graphql } from "gatsby"
import { GatsbyImage, getImage } from "gatsby-plugin-image"
function BlogPost({ data }) {
const image = getImage(data.blogPost.avatar)
return (
<section>
<h2>{data.blogPost.title}</h2>
<GatsbyImage image={image} alt={data.blogPost.author} />
<p>{data.blogPost.body}</p>
</section>
)
}
export const pageQuery = graphql`
query {
blogPost(id: { eq: $Id }) {
title
body
author
avatar {
childImageSharp {
gatsbyImageData(
width: 200
placeholder: BLURRED
formats: [AUTO, WEBP, AVIF]
)
}
}
}
}
`

Switch the language in React without using external libraries

What ways to change language in React can you suggest without using external libraries? My way is to use the ternary operator {language === 'en'? 'title': 'titre'}. If language is en, displaytitle if not, display titre. What other way can you recommend. For example, that the translations should be placed in a separate json file.
Code here: https://stackblitz.com/edit/react-eu9myn
class App extends Component {
constructor() {
super();
this.state = {
language: 'en'
};
}
changeLanguage = () => {
this.setState({
language: 'fr'
})
}
render() {
const {language} = this.state;
return (
<div>
<p>
{language === 'en' ? 'title' : 'titre'}
</p>
<button onClick={this.changeLanguage}>change language</button>
</div>
);
}
}

Internationalization (i18n) is a hard problem with a few existing, standard solutions designed by expert translators and linguists to account for the breadth of language quirks across the world. You shouldn't generally try to come up with your own solution, even when you are fluent in all target languages.
That doesn't mean you need a library (you could implement one of those standards yourself) but writing the i18n logic inline will not scale and probably won't work well.
The easiest case of i18n is if you're translating strings that do not depend on context and are complete sentences with no interpolation. You could get away with a very basic approach there, like using a big dictionary of translations and just looking up each string in it. It would look sort of like your ternary but at least it would scale for many languages, and it would be reasonable to do that with no library:
l10n = {
'title': {en: 'title', fr: 'titre'}
}
<p>
{l10n['title'][lang]}
</p>
However, if there is going to be string interpolation in your website/application/whatever, please consider a library that implements, say, ICU.
Now, let me show you why it would be a bad idea. Suppose you have the string "you can see (n) rocks" where you want to replace (n) with an actual number, and you want the sentence to be grammatically correct so you need to compute number agreement, right ? so, "0 rocks", "1 rock", "2+ rocks"… looks like English plural is just adding an "s" (not true, but let's assume for now), you could implement that with ternaries. I see you used French in your example so, how about that ? "0 cailloux", "1 caillou", "2+ cailloux". Right, there are multiple plural forms in French. How do you write your code to account for that ? And what if you need a German translation ? maybe the translator will decide that the object should go first in the sentence, rather than last. How does your code handle word order based on language ?
All these problems should be delegated to the translator who encodes them into an ICU string, which is then evaluated by some code given a context to get a correct translation. Whether you use a library or implement it yourself, what you want in the end is some function — let's call it localize(string, context) that is pretty much independent from React and that you use in your components like this:
import localize from './somewhere'
<p>
{localize('title')}
</p>
If you really want to, you can pass the locale as an argument and have it stored in React's state somehow. This library decided it wasn't necessary because real users rarely switch language and it's OK to reload the whole application when that happens.

I just implemented a simple language component for work that uses a Localisation context/provider and a dictionary (e.g JSON). I'll go through the steps, and there's a workable codesandbox example at the end. This is a very basic approach, but it works well for us at the moment.
The example has:
1) A simple "dictionary" that contains the tokens you want to translate in each language defined by a short code
{ EN: { welcome: 'Welcome' }, FR: { welcome: 'Bienvenue' }, IT: { welcome: 'Benvenuto' } };
2) An initial state and reducer that you can update when the language changes
export const initialState = {
defaultLanguage: 'EN',
selectedLanguage: 'IT'
}
export function reducer(state, action) {
const { type, payload } = action;
switch (type) {
case 'LANGUAGE_UPDATE': {
return { ...state, selectedLanguage: payload };
}
default: return state;
}
}
3) A Localisation Context/Provider. You can wrap your code in the provider and every child component can get access to the state through the context. We import the dictionary and state/reducer, create the new context and then set up the provider into which we pass the state and dictionary.
import dictionary from './dictionary';
import { initialState, reducer } from './localisationReducer';
export const LocalisationContext = React.createContext();
export function LocalisationProvider({ children }) {
const localisationStore = useReducer(reducer, initialState);
return (
<LocalisationContext.Provider value={{ localisationStore, dictionary }}>
{children}
</LocalisationContext.Provider>
);
}
4) An example app. You can see the LocalisationProvider wrapping the other elements, but also a dropdown, and a component called Translate. I'll describe those next.
<LocalisationProvider>
<Dropdown />
<div className="App">
<h1>
<Translate token="welcome" />
</h1>
<h2>Start editing to see some magic happen!</h2>
</div>
</LocalisationProvider>
5) The dropdown accesses the Localisation context and builds a dropdown with the languages. The key part is the handleSelected function which uses the dispatch from the localisation store to change the state (update the language):
import { LocalisationContext } from './localisation';
const langs = [
{ shortCode: 'EN', label: 'English' },
{ shortCode: 'FR', label: 'Français' },
{ shortCode: 'IT', label: 'Italiano' }
];
export function Dropdown() {
const {
localisationStore: [ state, dispatch ]
} = useContext(LocalisationContext);
const { selectedLanguage } = state;
const handleSelected = (e) => {
const { target: { value } } = e;
dispatch({ type: 'LANGUAGE_UPDATE', payload: value });
}
function getOptions(langs, selectedLanguage) {
return langs.map(({ shortCode, label }) => {
return <option value={shortCode}>{label}</option>
});
}
return (
<select onChange={handleSelected}>
{getOptions(langs, selectedLanguage)}
</select>
);
}
6) The Translate component which also accesses the state and dictionary through the context, and performs the translation based on the selected language.
import { LocalisationContext } from './localisation';
export default function Translator({ token }) {
const {
localisationStore: [state], dictionary
} = useContext(LocalisationContext);
const {
selectedLanguage, defaultLanguage
} = state;
const translatedToken = dictionary[selectedLanguage][token] || dictionary[defaultLanguage][token];
return (
<Fragment>
{translatedToken}
</Fragment>
);
}
Here's the codesandbox example for you to explore. Just select a new language from the dropdown to see the main "welcome" text change.