How to filter Sanity.io dataset based on a field on references - sanity

Question

How to get all posts by a category slug in GROQ?
You can see that a post is added to one or more categories. I would like to get all posts by a category slug to show the posts on a category page. I am new to Sanity.io's GROQ. All the tutorials I have found on creating a blog with sanity.io and next.js have not covered it to show a category page showing posts from a category.
Post schema:
export default {
name: 'post',
title: 'Post',
type: 'document',
fields: [
{
name: 'title',
title: 'Title',
type: 'string',
},
{
name: 'slug',
title: 'Slug',
type: 'slug',
options: {
source: 'title',
maxLength: 96,
},
},
{
name: 'author',
title: 'Author',
type: 'reference',
to: {type: 'author'},
},
{
name: 'mainImage',
title: 'Main image',
type: 'image',
options: {
hotspot: true,
},
},
{
name: 'categories',
title: 'Categories',
type: 'array',
of: [{type: 'reference', to: {type: 'category'}}],
},
{
name: 'publishedAt',
title: 'Published at',
type: 'datetime',
},
{
name: 'body',
title: 'Body',
type: 'blockContent',
},
],
preview: {
select: {
title: 'title',
author: 'author.name',
media: 'mainImage',
},
prepare(selection) {
const {author} = selection
return Object.assign({}, selection, {
subtitle: author && `by ${author}`,
})
},
},
}
I have tried the following:
const query = `*[_type == 'post' && $slug in [categories[]-> {slug}] ]{ _id, title, slug, publishedAt, categories[]-> {title,slug}} | order(publishedAt) [0...10]`;
const posts = await client.fetch(
query,
{ slug }
);
console.log("posts", posts);

Answer 1

I got the solution at Sanity's slack channel. The following code helps to get the posts from a category by it's slug.
`*[_type == 'post' && $slug in categories[]->slug.current ]`;