Problem with graphql resolvers using Lighthouse Graphql with Laravel

Question

:)

I am starting a new Laravel project with Lighthouse and have been problems with resolving non root fields.
According to the documentation here for each of the fields that have complex types, there should be a model and a query provided for the field.
So in this example I have a Version object which has two subfields: appVersion and apiVersion. Here is what I have in my schema.graphql file:

type Query {
    version: Version
}

type Version {
    appVersion: String
    apiVersion: String
}

And in addition, here is my model for Version:

<?php

namespace App\Models;

class Version {

    private string $appVersion;

    private string $apiVersion;

    public function __construct() {
        $composer = file_get_contents('../composer.json');
        $content = json_decode($composer, true);

        $this->appVersion = $content['app-version'];
        $this->apiVersion = $content['version'];
    }

    public function getAppVersion() : string {
        return $this->appVersion;
    }

    public function getApiVersion() : string {
        return $this->apiVersion;
    }

    function export() : array {
        return [
            'app' => $this->getAppVersion(),
            'api' => $this->getApiVersion(),
        ];
    }
}

And the Query file for Version:

<?php

namespace App\GraphQL\Queries;

use GraphQL\Type\Definition\ResolveInfo;
use Nuwave\Lighthouse\Support\Contracts\GraphQLContext;

final class Version {

    public function __invoke ($version, array $args, GraphQLContext $context, ResolveInfo $resolveInfo) {
        return $version->export()[$resolveInfo->fieldName];
    }
}

However the $version seems to be always null when I try to query version using the following:

{
  version {
    appVersion
  }
}

And I cannot figure our why. I tried to follow the docs as best as I could, but I am probably missing something really simple here :/ I should also mention that querying simple fields (like fields that don't have a sub selection) works here for me. Any help would be much appreciated :)

I implemented a graphql resolver, however the models were not resolved correctly.

score 2 · Answer 1 · answered Nov 22 '22 at 10:59

The App\GraphQL\Queries\Version::__invoke method is a field resolver. The first argument to that resolver is the root value. Think of it as the "parent" value from the query above that query in the tree. In your case, you query the version from the root "Query" type, so there is no value in the tree above. That is why it is null.

Your schema definition says "There is a model with properties appVersion and apiVersion". So your Version query should return an array or class with properties appVersion and apiVersion. It does not need to be an eloquent model.

<?php

namespace App\GraphQL\Queries;

use GraphQL\Type\Definition\ResolveInfo;
use Nuwave\Lighthouse\Support\Contracts\GraphQLContext;

final class Version {

    public function __invoke ($version, array $args, GraphQLContext $context, ResolveInfo $resolveInfo) {
        $composer = file_get_contents('../composer.json');
        $content = json_decode($composer, true);

        return [
            'appVersion' => $content['app-version'],
            'apiVersion' => $content['version'],
        ];
    }
}

score 1 · Answer 2 · answered Nov 22 '22 at 08:24

1

Add @field directive to your schema:

type Query {
    version: Version @field(resolver: "App\GraphQL\Queries\Version")
}

answered Nov 22 '22 at 08:24

mostafa

196
4

Problem with graphql resolvers using Lighthouse Graphql with Laravel

2 Answers2