How can I paginate a merged collection in Laravel 5?

Question

I am creating a stream which contains two types of objects, BluePerson and RedPerson. To create the stream, I fetch all of both objects, then merge them into one collection.

Answer 1

I had to deal with something like that in a project i was working on, where in one of the pages i had to display two type of publication paginated and sorted by the created_at field. In my case it was a Post model and an Event Model (hereinafter referred to as publications).

The only difference is i didn't want to get all the publications from database then merge and sort the results, as you can imagine it would rise a performance issue if we have hundreds of publications.

So i figure out that it would be more convenient to paginate each model and only then, merge and sort them.

So here is what i did (based on answers and comments posted earlier)

First of all let me show you a simplified version of "my solution", then i will try to explain the code as much as i could.

use App\Models\Post;
use App\Models\Event;
use App\Facades\Paginator;


class PublicationsController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @param \Illuminate\Http\Request $request
     * @return \Illuminate\Http\Response
     */
    public function index(Request $request)
    {
        $events       = Event::latest()->paginate(5);
        $posts        = Post::latest()->paginate(5);

        $publications = Paginator::merge($events, $posts)->sortByDesc('created_at')->get();

        return view('publications.index', compact('publications'));
    }
}

As you can guess it by now, the facade Paginator is the responsible of merging and sorting my paginators ($events & $posts)

To make this answer a little bit more clear and complete, i will show you how to create your own Facade.

You can choose to put your own facades anywhere you like, personally, i choose to put them inside Facades folder under the app folder, just like shown in this tree.

+---app
|   +---Console
|   +---Events
|   +---Exceptions
|   +---Exports
|   +---Facades
|   |   +---Paginator.php
|   |   +---...
|   +---Http
|   |   +---Controllers
.   .   +---...
.   .   .

Put this code inside app/Facades/Paginator.php

namespace App\Facades;

use Illuminate\Support\Facades\Facade;

class Paginator extends Facade
{
    /**
     * Get the registered name of the component.
     *
     * @return string
     */
    protected static function getFacadeAccessor()
    {
        return 'paginator';
    }
}

For more info, you can see How Facades Work

Next, bind paginator to service container, open app\Providers\AppServiceProvider.php

namespace App\Providers;

use App\Services\Pagination\Paginator;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        $this->app->bind('paginator', function ($app) {

            return new Paginator;
        });
    }
}

For more info, you can see The Boot Method

My Paginator class is under app/Services/Pagination/ folder. Again, you can put your classes wherever you like.

namespace App\Services\Pagination;

use Illuminate\Support\Arr;
use InvalidArgumentException;
use Illuminate\Support\Collection;
use Illuminate\Pagination\LengthAwarePaginator;

class Paginator
{
    /**
     * All of the items being paginated.
     *
     * @var \Illuminate\Support\Collection
     */
    protected $items;

    /**
     * The number of items to be shown per page.
     *
     * @var int
     */
    protected $perPage;

    /**
     * The total number of items before slicing.
     *
     * @var int
     */
    protected $total;

    /**
     * The base path to assign to all URLs.
     *
     * @var string
     */
    protected $path = '/';


    /**
     * Merge paginator instances
     *
     * @param  mixed $paginators
     * @param  bool  $descending
     * @return \Illuminate\Pagination\LengthAwarePaginator
     */
    function merge($paginators)
    {
        $paginators = is_array($paginators) ? $paginators : func_get_args();

        foreach ($paginators as $paginator) {
            if (!$paginator instanceof LengthAwarePaginator) {
                throw new InvalidArgumentException("Only LengthAwarePaginator may be merged.");
            }
        }

        $total   = array_reduce($paginators, function($carry, $paginator) {

            return $paginator->total();
        }, 0);

        $perPage = array_reduce($paginators, function($carry, $paginator) {

            return $paginator->perPage();
        }, 0);

        $items   = array_map(function($paginator) {

            return $paginator->items();

        }, $paginators);

        $items         = Arr::flatten($items);

        $items         = Collection::make($items);

        $this->items   = $items;
        $this->perPage = $perPage;
        $this->total   = $total;

        return $this;
    }

    /**
     * Sort the collection using the given callback.
     *
     * @param  callable|string  $callback
     * @param  int  $options
     * @param  bool  $descending
     * @return static
     */
    public function sortBy($callback, $options = SORT_REGULAR, $descending = false)
    {
        $this->items = $this->items->sortBy($callback, $options, $descending);

        return $this;
    }

    /**
     * Sort the collection in descending order using the given callback.
     *
     * @param  callable|string  $callback
     * @param  int  $options
     * @return static
     */
    public function sortByDesc($callback, $options = SORT_REGULAR)
    {
        return $this->sortBy($callback, $options, true);
    }

    /**
     * Get paginator
     *
     * @return \Illuminate\Pagination\LengthAwarePaginator
     */
    public function get()
    {
        return new LengthAwarePaginator(
            $this->items,
            $this->total,
            $this->perPage,
            LengthAwarePaginator::resolveCurrentPage(),
            [
                'path' => LengthAwarePaginator::resolveCurrentPath(),
            ]
        );
    }
}

---

Definitely there is room for improvements, so please if you see something that needs to be changed, leave a comment here or reach me on twitter.