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Relay Library for graphql-php

This is a library to allow the easy creation of Relay-compliant servers using the graphql-php reference implementation of a GraphQL server.

Note: The code is a port of the original graphql-relay js implementation from Facebook (With some minor PHP related adjustments and extensions)

Current Status:

The basic functionality with the helper functions is in place along with the tests. Only the asynchronous functionality was not yet ported due to the limitations of PHP. See also discussions here and here

Getting Started

A basic understanding of GraphQL and of the graphql-php implementation is needed to provide context for this library.

An overview of GraphQL in general is available in the README for the Specification for GraphQL.

This library is designed to work with the graphql-php reference implementation of a GraphQL server.

An overview of the functionality that a Relay-compliant GraphQL server should provide is in the GraphQL Relay Specification on the Relay website. That overview describes a simple set of examples that exist as tests in this repository. A good way to get started with this repository is to walk through that documentation and the corresponding tests in this library together.

Using Relay Library for graphql-php

Install this repository via composer:

composer require ivome/graphql-relay-php

When building a schema for graphql-php, the provided library functions can be used to simplify the creation of Relay patterns.

Connections

Helper functions are provided for both building the GraphQL types for connections and for implementing the resolve method for fields returning those types.

• Relay::connectionArgs returns the arguments that fields should provide when they return a connection type that supports bidirectional pagination.
• Relay::forwardConnectionArgs returns the arguments that fields should provide when they return a connection type that only supports forward pagination.
• Relay::backwardConnectionArgs returns the arguments that fields should provide when they return a connection type that only supports backward pagination.
• Relay::connectionDefinitions returns a connectionType and its associated edgeType, given a node type.
• Relay::edgeType returns a new edgeType
• Relay::connectionType returns a new connectionType
• Relay::connectionFromArray is a helper method that takes an array and the arguments from connectionArgs, does pagination and filtering, and returns an object in the shape expected by a connectionType's resolve function.
• Relay::cursorForObjectInConnection is a helper method that takes an array and a member object, and returns a cursor for use in the mutation payload.

An example usage of these methods from the test schema:

$shipConnection = Relay::connectionDefinitions([
    'nodeType' => $shipType
]);

// this could also be written as
//
// $shipEdge = Relay::edgeType([
//     'nodeType' => $shipType
// ]);
// $shipConnection = Relay::connectionType([
//     'nodeType' => $shipType,
//     'edgeType' => $shipEdge
// ]);

$factionType = new ObjectType([
    'name' => 'Faction',
    'description' => 'A faction in the Star Wars saga',
    'fields' => function() use ($shipConnection) {
        return [
            'id' => Relay::globalIdField(),
            'name' => [
                'type' => Type::string(),
                'description' => 'The name of the faction.'
            ],
            'ships' => [
                'type' => $shipConnection['connectionType'],
                'description' => 'The ships used by the faction.',
                'args' => Relay::connectionArgs(),
                'resolve' => function($faction, $args) {
                    // Map IDs from faction back to ships
                    $data = array_map(function($id) {
                        return StarWarsData::getShip($id);
                    }, $faction['ships']);
                    return Relay::connectionFromArray($data, $args);
                }
            ]
        ];
    },
    'interfaces' => [$nodeDefinition['nodeInterface']]
]);

This shows adding a ships field to the Faction object that is a connection. It uses connectionDefinitions({nodeType: shipType}) to create the connection type, adds connectionArgs as arguments on this function, and then implements the resolve function by passing the array of ships and the arguments to connectionFromArray.

Object Identification

Helper functions are provided for both building the GraphQL types for nodes and for implementing global IDs around local IDs.

• Relay::nodeDefinitions returns the Node interface that objects can implement, and returns the node root field to include on the query type. To implement this, it takes a function to resolve an ID to an object, and to determine the type of a given object.
• Relay::toGlobalId takes a type name and an ID specific to that type name, and returns a "global ID" that is unique among all types.
• Relay::fromGlobalId takes the "global ID" created by toGlobalID, and returns the type name and ID used to create it.
• Relay::globalIdField creates the configuration for an id field on a node.
• Relay::pluralIdentifyingRootField creates a field that accepts a list of non-ID identifiers (like a username) and maps then to their corresponding objects.

An example usage of these methods from the test schema:

$nodeDefinition = Relay::nodeDefinitions(
    // The ID fetcher definition
    function ($globalId) {
        $idComponents = Relay::fromGlobalId($globalId);
        if ($idComponents['type'] === 'Faction'){
            return StarWarsData::getFaction($idComponents['id']);
        } else if ($idComponents['type'] === 'Ship'){
            return StarWarsData::getShip($idComponents['id']);
        } else {
            return null;
        }
    },
    // Type resolver
    function ($object) {
        return isset($object['ships']) ? self::getFactionType() : self::getShipType();
    }
);

$factionType = new ObjectType([
    'name' => 'Faction',
    'description' => 'A faction in the Star Wars saga',
    'fields' => function() use ($shipConnection) {
        return [
            'id' => Relay::globalIdField(),
            'name' => [
                'type' => Type::string(),
                'description' => 'The name of the faction.'
            ],
            'ships' => [
                'type' => $shipConnection['connectionType'],
                'description' => 'The ships used by the faction.',
                'args' => Relay::connectionArgs(),
                'resolve' => function($faction, $args) {
                    // Map IDs from faction back to ships
                    $data = array_map(function($id) {
                        return StarWarsData::getShip($id);
                    }, $faction['ships']);
                    return Relay::connectionFromArray($data, $args);
                }
            ]
        ];
    },
    'interfaces' => [$nodeDefinition['nodeInterface']]
]);

$queryType = new ObjectType([
    'name' => 'Query',
    'fields' => function () use ($nodeDefinition) {
        return [
            'node' => $nodeDefinition['nodeField']
        ];
    },
]);

This uses Relay::nodeDefinitions to construct the Node interface and the node field; it uses fromGlobalId to resolve the IDs passed in in the implementation of the function mapping ID to object. It then uses the Relay::globalIdField method to create the id field on Faction, which also ensures implements the nodeInterface. Finally, it adds the node field to the query type, using the nodeField returned by Relay::nodeDefinitions.

Mutations

A helper function is provided for building mutations with single inputs and client mutation IDs.

• Relay::mutationWithClientMutationId takes a name, input fields, output fields, and a mutation method to map from the input fields to the output fields, performing the mutation along the way. It then creates and returns a field configuration that can be used as a top-level field on the mutation type.

An example usage of these methods from the test schema:

$shipMutation = Relay::mutationWithClientMutationId([
    'name' => 'IntroduceShip',
    'inputFields' => [
        'shipName' => [
            'type' => Type::nonNull(Type::string())
        ],
        'factionId' => [
            'type' => Type::nonNull(Type::id())
        ]
    ],
    'outputFields' => [
        'ship' => [
            'type' => $shipType,
            'resolve' => function ($payload) {
                return StarWarsData::getShip($payload['shipId']);
            }
        ],
        'faction' => [
            'type' => $factionType,
            'resolve' => function ($payload) {
                return StarWarsData::getFaction($payload['factionId']);
            }
        ]
    ],
    'mutateAndGetPayload' => function ($input) {
        $newShip = StarWarsData::createShip($input['shipName'], $input['factionId']);
        return [
            'shipId' => $newShip['id'],
            'factionId' => $input['factionId']
        ];
    }
]);

$mutationType = new ObjectType([
    'name' => 'Mutation',
    'fields' => function () use ($shipMutation) {
        return [
            'introduceShip' => $shipMutation
        ];
    }
]);

This code creates a mutation named IntroduceShip, which takes a faction ID and a ship name as input. It outputs the Faction and the Ship in question. mutateAndGetPayload then gets an object with a property for each input field, performs the mutation by constructing the new ship, then returns an object that will be resolved by the output fields.

Our mutation type then creates the introduceShip field using the return value of Relay::mutationWithClientMutationId.

Contributing

After cloning this repo, ensure dependencies are installed by running:

composer install

After developing, the full test suite can be evaluated by running:

bin/phpunit tests