Laravel/ Lighthouse GraphQL - how to find by slug attribute?

Question

I'm creating a Laravel backend for a Nuxt app, and am using Lighthouse-PHP to deliver data via GraphQL.

I'm trying to set up a query to do a find by slug instead of the default ID. When I run the query in the graphql playground, it correctly returns the data, however when I load the page on the frontend, it returns null.

Backend

schema.graphql

type Query {
  forumCategoryBySlug(slug: String! @eq): ForumCategory @find
}

type ForumCategory {
  id: ID!
  title: String!
  description: String!
  slug: String!
  subcategories: [ForumSubcategory!]! @hasMany
  created_at: DateTime!
  updated_at: DateTime!
}

ForumCategory.php model

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;

class ForumCategory extends Model
{
    protected $fillable = [
        'title', 'description', 'slug'
    ];

    public function subcategories(): HasMany
    {
        return $this->hasMany(ForumSubcategory::class);
    }
}

Frontend

Index.vue

import categoryQuery from '~/apollo/queries/forum/category.gql';
export default {
  apollo: {
    category: {
      prefetch: false,
      fetchPolicy: 'network-only',
      query: categoryQuery,
      variables () {
        return {
          slug: this.$route.params.slug
        };
      }
    }
  },
}

category.gql

query Category($slug: String!) {
  category: forumCategoryBySlug(slug: $slug) {
    id
    title
    description
    slug
  }
}

I feel like I've triple-checked every little thing but can't for the life of me figure out why the data is still returning null. Any help would be greatly appreciated!

Answer 1

Figured it out after a few days. Essentially I needed to create a custom resolver.

schema.graphql

type Query {
  forumCategoryBySlug(slug: String! @eq): ForumCategory
}

app/GraphQL/Queries/ForumCategoryBySlug.php

<?php

namespace App\GraphQL\Queries;
use App\Models\ForumCategory;

class ForumCategoryBySlug
{
    /**
     * @param  null  $_
     * @param  array<string, mixed>  $args
     */
    public function __invoke($_, array $args)
    {
        $category = \App\Models\ForumCategory::findBySlug($args["slug"])->first();
        return $category;
    }
}