How do I query my API for a single entity by its "slug" with GraphQL? - graphql

Question

I am creating a Next.js blog that uses an API created with KeystoneJS. I am extremely confused by how I can get an individual post on a dynamic route from the post's slug.
The Query
This is how I thought the query should be:
query Post($slug: String) {
Post(where: { slug: $slug }) {
id
}
}
And this was queried like so in a file called post.service.js:
export async function getBySlug(slug) {
return apolloClient
.query({
query: gql`
query Post($slug: String) {
Post(where: { slug: $slug }) {
id
}
}
`,
})
.then((result) => {
return result.data.Post;
});
}
Unsurprisingly, that causes an ApolloError because how would the query know what slug to query the API for when accessing posts/[slug].js?
It's also worth noting that KeystoneJS say on their guides that:
The single entity query accepts a where parameter which must provide an id.
How would I pass the post's ID to the query depending on what slug was accessed at [slug].js and does this mean I can't query by the slug at all?
On [slug].js I am using getStaticPaths() and getStaticProps() like this:
export async function getStaticPaths() {
const posts = await getAll();
const paths = posts.map((post) => ({
params: { slug: post.slug },
}));
return { paths, fallback: false };
}
export async function getStaticProps({ params }) {
const term = await getBySlug(params.slug);
return { props: { post } };
}
How can I do this?

Answer 1

If you're using a where clause rather than matching on id, you have to query allPosts rather than Post.
A tested example, matching a user by their email address:
query($email: String!) {
allUsers(where : {email: $email}){
id
}
}
Variables:
{
"email": "user#email.com"
}
So I think you want:
query($slug: String!) {
allPosts(where: {slug: $slug}) {
id
}
}