Expression language

All definition config entries can use expression language but it must be explicitly triggered using "@=" like prefix.

Functions description:

Expression	Description	Usage	Alias
object service(string $id)	Get a service from the container	@=service('my_service').customMethod()	serv
mixed parameter(string $name)	Get parameter from the container	@=parameter('kernel.debug')	param
boolean isTypeOf(string $className)	Verified if value is instance of className	@=isTypeOf('AppBundle\User\User')
mixed resolver(string $alias, array$args = [])	call the method on the tagged service "overblog_graphql.resolver" with args	@=resolver('blog_by_id', [value['blogID']]	res
mixed mutation(string $alias, array$args = [])	call the method on the tagged service "overblog_graphql.mutation" with args	@=mutation('remove_post_from_community', [value])	mut
mixed arguments(array $mapping, mixed$data)	Transform and validate a list of arguments. Arguments Transformer	@=arguments({ 'input': 'MyInput' }, {'input': { 'field1': "value1" }])
string globalId(string|int id, string $typeName = null)	Relay node globalId	@=globalId(15, 'User')
array fromGlobalId(string $globalId)	Relay node fromGlobalId	@=fromGlobalId('QmxvZzox')
object newObject(string $className, array$args = [])	Instantiation $className object with$args	@=newObject('AppBundle\User\User', ['John', 15])
mixed call(mixed $target, array$args = [])	Call the target method with given $args	@=call(service('my_service').method, ["arg1", 2])
boolean hasRole(string $role)	Checks whether the token has a certain role.	@=hasRole('ROLE_API')
boolean hasAnyRole(string $role1, string$role2, ...string $roleN)	Checks whether the token has any of the given roles.	@=hasAnyRole('ROLE_API', 'ROLE_ADMIN')
boolean isAnonymous()	Checks whether the token is anonymous.	@=isAnonymous()
boolean isRememberMe()	Checks whether the token is remember me.	@=isRememberMe()
boolean isFullyAuthenticated()	Checks whether the token is fully authenticated.	@=isFullyAuthenticated()
boolean isAuthenticated()	Checks whether the token is not anonymous.	@=isAuthenticated()
boolean hasPermission(mixed $var, string$permission)	Checks whether the token has the given permission for the given object (requires the ACL system).	@=hasPermission(object, 'OWNER')
boolean hasAnyPermission(mixed $var, array$permissions)	Checks whether the token has any of the given permissions for the given object	@=hasAnyPermission(object, ['OWNER', 'ADMIN'])
User getUser()	Returns the user which is currently in the security token storage. User can be null.	@=getUser()

Variables description:

Expression	Description	Scope
typeResolver	the type resolver	global
object	Refers to the value of the field for which access is being requested. For array object will be each item of the array. For Relay connection object will be the node of each connection edges.	only available for config.fields.*.access with query operation or mutation payload type.
value	Resolver value	only available in resolve context
args	Resolver args array	only available in resolve context
info	Resolver GraphQL\Type\Definition\ResolveInfo Object	only available in resolve context
context	context is defined by your application on the top level of query execution (useful for storing current user, environment details, etc)	only available in resolve context
childrenComplexity	Selection field children complexity	only available in complexity context

For more details on expression syntax

Private services

It is not possible to use private services with service or serv functions since this is equivalent to call get method on the container. Private services must be tag as global variable to be accessible.

Yaml example:

App\MyPrivateService:
    public: false
    tags:
        - { name: overblog_graphql.global_variable, alias: my_private_service }

To use a vendor private services:

<?php

$vendorPrivateServiceDef = $container->findDefinition(\Vendor\PrivateService::class);
$vendorPrivateServiceDef->addTag('overblog_graphql.global_variable', ['alias' => 'vendor_private_service']);

Usage:

MyType:
    type: object
    config:
        fields:
            name:
                type: String!
                resolve: '@=my_private_service.formatName(value)'

Custom expression function

Adding custom expression function is easy since all you need to do is create a tagged service. Expression functions can help user create simple resolver without having to leave config file, this also improves performance by removing a useless external resolver call.

Here is an example to add a custom expression equivalent to php json_decode:

<?php

namespace App\ExpressionLanguage;

use Overblog\GraphQLBundle\ExpressionLanguage\ExpressionFunction;

class JsonDecode extends ExpressionFunction
{
    public function __construct()
    {
        parent::__construct(
            'json_encode',
            function ($json, $assoc) {
                return sprintf('json_decode(%s, %s)', $json, $assoc);
            }
        );
    }
}

now register your service

App\ExpressionLanguage\JsonDecode:
    tags: ['overblog_graphql.expression_function']

Now json_decode can be used in schema:

Object:
    type: object
    config:
        fields:
            name:
            type: String!
            resolve: "@=json_decode(value.json_data, true)['name']"

Tips: At last if this is not an answer to all your needs, the expression language service can be customized using bundle configuration.