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expression-language.md

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Expression language

All definitions configs 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
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])
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

Custom expression function is easy as creating a tagged service. Adding useful expression function can help user create simple resolver without having to leave config file, this also improve performance by removing a useless external resolver call.

Here an example to add an 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 use in schema:

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

Tips: At last if this is till no answer to all your needs, the expression language service can be custom using bundle configuration.