Custom types

In some special cases, you want to override the GraphQL return type that is attributed by default by GraphQLite.

For instance:

#[Type(class: Product::class)]
class ProductType
{
    #[Field]
    public function getId(Product $source): string
    {
        return $source->getId();
    }
}

In the example above, GraphQLite will generate a GraphQL schema with a field id of type string:

type Product {
    id: String!
}

GraphQL comes with an ID scalar type. But PHP has no such type. So GraphQLite does not know when a variable is an ID or not.

You can help GraphQLite by manually specifying the output type to use:

    #[Field(outputType: "ID")]

Usage

The outputType attribute will map the return value of the method to the output type passed in parameter.

You can use the outputType attribute in the following annotations:

• #[Query]
• #[Mutation]
• #[Subscription]
• #[Field]
• #[SourceField]
• #[MagicField]

Registering a custom output type (advanced)

In order to create a custom output type, you need to:

1. Design a class that extends GraphQL\Type\Definition\ObjectType.
2. Register this class in the GraphQL schema.

You'll find more details on the Webonyx documentation.

---

In order to find existing types, the schema is using type mappers (classes implementing the TypeMapperInterface interface).

You need to make sure that one of these type mappers can return an instance of your type. The way you do this will depend on the framework you use.

Symfony users

Any class extending GraphQL\Type\Definition\ObjectType (and available in the container) will be automatically detected by Symfony and added to the schema.

If you want to automatically map the output type to a given PHP class, you will have to explicitly declare the output type as a service and use the graphql.output_type tag:

# config/services.yaml
services:
    App\MyOutputType:
        tags:
            - { name: 'graphql.output_type', class: 'App\MyPhpClass' }

Other frameworks

The easiest way is to use a StaticTypeMapper. Use this class to register custom output types.

// Sample code:
$staticTypeMapper = new StaticTypeMapper(
    // Let's register a type that maps by default to the "MyClass" PHP class
    types: [
        MyClass::class => new MyCustomOutputType()
    ],

    // If you don't want your output type to map to any PHP class by default, use:
    notMappedTypes: [
        new MyCustomOutputType()
    ],
);

// Register the static type mapper in your application using the SchemaFactory instance
$schemaFactory->addTypeMapper($staticTypeMapper);

Registering a custom scalar type (advanced)

If you need to add custom scalar types, first, check the GraphQLite Misc. Types library. It contains a number of "out-of-the-box" scalar types ready to use and you might find what you need there.

You still need to develop your custom scalar type? Ok, let's get started.

In order to add a scalar type in GraphQLite, you need to:

• create a Webonyx custom scalar type. You do this by creating a class that extends GraphQL\Type\Definition\ScalarType.
• create a "type mapper" that will map PHP types to the GraphQL scalar type. You do this by writing a class implementing the RootTypeMapperInterface.
• create a "type mapper factory" that will be in charge of creating your "type mapper".

interface RootTypeMapperInterface
{
    /**
     * @param \ReflectionMethod|\ReflectionProperty $reflector
     */
    public function toGraphQLOutputType(Type $type, ?OutputType $subType, $reflector, DocBlock $docBlockObj): OutputType;

    /**
     * @param \ReflectionMethod|\ReflectionProperty $reflector
     */
    public function toGraphQLInputType(Type $type, ?InputType $subType, string $argumentName, $reflector, DocBlock $docBlockObj): InputType;

    public function mapNameToType(string $typeName): NamedType;
}

The toGraphQLOutputType and toGraphQLInputType are meant to map a return type (for output types) or a parameter type (for input types) to your GraphQL scalar type. Return your scalar type if there is a match or null if there no match.

The mapNameToType should return your GraphQL scalar type if $typeName is the name of your scalar type.

RootTypeMapper are organized in a chain (they are actually middlewares). Each instance of a RootTypeMapper holds a reference on the next root type mapper to be called in the chain.

For instance:

class AnyScalarTypeMapper implements RootTypeMapperInterface
{
    /** @var RootTypeMapperInterface */
    private $next;

    public function __construct(RootTypeMapperInterface $next)
    {
        $this->next = $next;
    }

    public function toGraphQLOutputType(Type $type, ?OutputType $subType, ReflectionMethod $refMethod, DocBlock $docBlockObj): ?OutputType
    {
        if ($type instanceof Scalar) {
            // AnyScalarType is a class implementing the Webonyx ScalarType type.
            return AnyScalarType::getInstance();
        }
        // If the PHPDoc type is not "Scalar", let's pass the control to the next type mapper in the chain
        return $this->next->toGraphQLOutputType($type, $subType, $refMethod, $docBlockObj);
    }

    public function toGraphQLInputType(Type $type, ?InputType $subType, string $argumentName, ReflectionMethod $refMethod, DocBlock $docBlockObj): ?InputType
    {
        if ($type instanceof Scalar) {
            // AnyScalarType is a class implementing the Webonyx ScalarType type.
            return AnyScalarType::getInstance();
        }
        // If the PHPDoc type is not "Scalar", let's pass the control to the next type mapper in the chain
        return $this->next->toGraphQLInputType($type, $subType, $argumentName, $refMethod, $docBlockObj);
    }

    /**
     * Returns a GraphQL type by name.
     * If this root type mapper can return this type in "toGraphQLOutputType" or "toGraphQLInputType", it should
     * also map these types by name in the "mapNameToType" method.
     *
     * @param string $typeName The name of the GraphQL type
     * @return NamedType|null
     */
    public function mapNameToType(string $typeName): ?NamedType
    {
        if ($typeName === AnyScalarType::NAME) {
            return AnyScalarType::getInstance();
        }
        return null;
    }
}

Now, in order to create an instance of your AnyScalarTypeMapper class, you need an instance of the $next type mapper in the chain. How do you get the $next type mapper? Through a factory:

class AnyScalarTypeMapperFactory implements RootTypeMapperFactoryInterface
{
    public function create(RootTypeMapperInterface $next, RootTypeMapperFactoryContext $context): RootTypeMapperInterface
    {
        return new AnyScalarTypeMapper($next);
    }
}

Now, you need to register this factory in your application, and we are done.

You can register your own root mapper factories using the SchemaFactory::addRootTypeMapperFactory() method.

$schemaFactory->addRootTypeMapperFactory(new AnyScalarTypeMapperFactory());

If you are using the Symfony bundle, the factory will be automatically registered, you have nothing to do (the service is automatically tagged with the "graphql.root_type_mapper_factory" tag).