# Resolvers

# Resolver function signature

Resolvers are always called with the same 4 arguments:

<?php

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

public function resolve(
    $rootValue,
    array $args,
    GraphQLContext $context,
    ResolveInfo $resolveInfo
)

1. $rootValue: The result that was returned from the parent field. When resolving a field that sits on one of the root types (Query, Mutation) this is null.
2. array $args: The arguments that were passed into the field. For example, for a field call like user(name: "Bob") it would be ['name' => 'Bob']
3. GraphQLContext $context: Arbitrary data that is shared between all fields of a single query. Lighthouse passes in an instance of Nuwave\Lighthouse\Schema\Context by default.
4. ResolveInfo $resolveInfo: Information about the query itself, such as the execution state, the field name, path to the field from the root, and more.

# Complexity function signature

The complexity function is used to calculate a query complexity score for a field. You can define your own complexity function with the @complexity directive.

<?php

public function complexity(int $childrenComplexity, array $args): int

1. $childrenComplexity: The complexity of the children of the field. In case you expect to return multiple children, it can be useful to do some maths on this.
2. array $args: The arguments that were passed into the field. For example, for a field call like user(name: "Bob") it would be ['name' => 'Bob']

Read more about query complexity in the [webonyx/graphql-php docs](Read More)