wwwision/relay-pagination

Simple pagination implementing the Cursor Connections Specification, see https://relay.dev/graphql/connections.htm

1.1.0 2021-07-16 15:40 UTC

This package is auto-updated.

Last update: 2022-05-16 17:33:01 UTC


README

Simple pagination implementing the Cursor Connections Specification, see https://relay.dev/graphql/connections.htm

Installation

Install via composer:

composer require wwwision/relay-pagination

Usage

$loader = # ... instance of \Wwwision\RelayPagination\Loader\Loader
$resultsPerPage = 5; // edges to load per page

$paginator = new Paginator($loader);
$firstPage = $paginator->first($resultsPerPage);

foreach ($firstPage as $edge) {
    // $edge->cursor(); contains the cursor string
    // $edge->node(); contains the payload
}

// $firstPage->pageInfo(); contains an object with pagination information

Next page(s)

Every connection contains information about next and previous pages. To navigate to a succeeding page, you can use the endCursor of the previous connection as input for the after argument:

if ($firstPage->pageInfo()->hasNextPage()) {
  $secondPage = $paginator->first($resultsPerPage, $firstPage->pageInfo()->endCursor());
  // ...
}

Backwards navigation

To navigate to a preceeding page, the startCursor can be passed to the last() method likewise:

if ($secondPage->pageInfo()->hasPreviousPage()) {
  $firstPage = $paginator->last($resultsPerPage, $secondPage->pageInfo()->startCursor());
  // ...
}

Reversed order

The ordering of edges is the same whether forward or backward navigation is used (as defined in the specification). To navigate through results in reversed order, the reversed() method of the Paginator can be used:

$loader = new ArrayLoader(range('a', 'e'));
$paginator = (new Paginator($loader))->reversed();

$page1 = $paginator->first(3);

Assert::same(['e', 'd', 'c'], array_map(fn($edge) => $edge->node(), $page1->toArray()));
Assert::false($page1->pageInfo()->hasPreviousPage());
Assert::true($page1->pageInfo()->hasNextPage());

$page2 = $paginator->first(3, $page1->pageInfo()->endCursor());
Assert::same(['b', 'a'], array_map(fn($edge) => $edge->node(), $page2->toArray()));
Assert::true($page2->pageInfo()->hasPreviousPage());
Assert::false($page2->pageInfo()->hasNextPage());

Loaders

This package comes with three adapters (aka "loaders"):

ArrayLoader

The ArrayLoader allows to paginate arbitrary arrays. Note: This loader is mainly meant for testing and debugging purposes and it should not be used for large datasets because the whole array has to be loaded into memory, obviously.

Usage

$arrayLoader = new ArrayLoader($arbitraryArray);

Note: The specified array can be associative, but the keys will be lost during pagination since the ArrayLoader only works with the array values in order to guarantee deterministic ordering.

CallbackLoader

The CallbackLoader invokes closures to determine pagination results. Note: This loader is mainly meant for rapid development, testing & debugging purposes. Usually you'd want to create a custom implementation of the Loader interface instead

Usage

$callbackLoader = new CallbackLoader(
    fn(int $limit, string $startCursor = null) => Edges::fromRawArray(...),
    fn(int $limit, string $endCursor = null) => Edges::fromRawArray(...)
);

DbalLoader

The DbalLoader allows to paginate arbitrary DBAL results. Note: This loader requires the doctrine/dbal package to be installed:

composer require doctrine/dbal

Usage

$queryBuilder = (new QueryBuilder($dbalConnection))
  ->select('*')
  ->from('some_table');
$dbalLoader = new DbalLoader($queryBuilder, 'id');

Convert nodes

A node is the only untyped property in this package since the loaders define the structure & type of nodes. For the DbalLoader a node is an associative array containing the raw result from the corresponding database row for example.

In order to make it easier to re-use loaders a Node Converter can be specified that is applied to all results before it is returned:

$paginator = (new Paginator($someLoader))
  ->withNodeConverter(fn(string $node) => json_decode($node));

The above example expects the nodes to contain a valid JSON string. The same mechanism can be used in order to convert database results to a dedicated domain model instance:

$paginator = (new Paginator($dbalLoader))
  ->withNodeConverter(fn(array $row) => MyModel::fromDatabaseRow($row));

Examples

See examples folder