too long

I am using the laravel framework and I am with the following problem:

ErrorException in 26f94b8c1c08197a35c59fdc230bbd6f line 5: Trying to get property of non-object (View: C:\Users\xxx\Desktop\PHP\laravelesources\views\exemplo.blade.php)

WelcomeController.php:

<?php

namespace CodeCommerce\Http\Controllers;

use CodeCommerce\Category; // Importando o Model Category

use Illuminate\Http\Request;

use CodeCommerce\Http\Requests;
use CodeCommerce\Http\Controllers\Controller;


class WelcomeController extends Controller
{
    private $categories;

    public function __construct(Category $categories)
    {
        $this->categories = $categories;
    }

    public function exemplo()
    {
        $categories = $this->categories;

        return view('exemplo', compact('categories'));
    }
}

Exemplo.blade.php:

<h1>Exemplo</h1>

<ul>
    @foreach($categories as $category)
        <li>{{ $category->name }}</li>
    @endforeach
</ul>

Model --- Category.php:

<?php

namespace CodeCommerce;

use Illuminate\Database\Eloquent\Model;

class Category extends Model
{
    //
}

I have the answer, just called the method all ();

public function exemplo()
{
    $categories = $this->categories->all();

    return view('exemplo', compact('categories'));
}