Field Resolvers

A FieldResolver resolves a single GraphQL field. Each resolver is a focused class with one responsibility: given a root value, arguments, and request context, return the field's value.

The Interface

interface FieldResolver
{
    public function resolve(mixed $rootValue, array $args, ResolverContext $context): mixed;
}

• $rootValue — the parent object (e.g. for Book.author, this is the Book array or object).
• $args — the field's inline arguments as an associative array.
• $context — carries the current Request for auth checks, header reads, etc.

Basic Example

A resolver for Query.books that returns a static list:

<?php

use PHPNomad\GraphQL\Interfaces\FieldResolver;
use PHPNomad\GraphQL\Interfaces\ResolverContext;

final class BooksResolver implements FieldResolver
{
    public function resolve(mixed $rootValue, array $args, ResolverContext $context): mixed
    {
        return [
            ['id' => '1', 'title' => 'The Pragmatic Programmer'],
            ['id' => '2', 'title' => 'Clean Code'],
        ];
    }
}

Using Arguments

A resolver for Query.book(id: ID!) that looks up a single book:

<?php

use PHPNomad\GraphQL\Interfaces\FieldResolver;
use PHPNomad\GraphQL\Interfaces\ResolverContext;

final class BookByIdResolver implements FieldResolver
{
    public function resolve(mixed $rootValue, array $args, ResolverContext $context): mixed
    {
        return $this->books->find($args['id']);
    }
}

Using the Request Context

$context->getRequest() gives you access to the full Request object — useful for reading auth tokens, user info, or custom headers:

final class ViewerResolver implements FieldResolver
{
    public function resolve(mixed $rootValue, array $args, ResolverContext $context): mixed
    {
        $request = $context->getRequest();
        $user = $request->getUser();

        if ($user === null) {
            return null;
        }

        return ['id' => $user->getId(), 'email' => $user->getEmail()];
    }
}

Injecting Services

Resolvers are resolved from the DI container at query time, so you can declare service dependencies in the constructor:

final class BooksResolver implements FieldResolver
{
    public function __construct(private readonly BookRepository $books) {}

    public function resolve(mixed $rootValue, array $args, ResolverContext $context): mixed
    {
        return $this->books->findAll();
    }
}

Bind your resolver in an initializer's getClassDefinitions() if it needs interface-to-concrete wiring:

public function getClassDefinitions(): array
{
    return [
        EloquentBookRepository::class => BookRepository::class,
    ];
}

Registering Resolvers

Resolvers are referenced by class-string in a TypeDefinition's getResolvers() map. You don't register them anywhere else — the strategy reads the map and calls $container->get(ResolverClass::class) when the field is requested. See Type Definitions for the full example.