php_laravel_laracasts/app/Mail/Welcome.php

<?php

namespace App\Mail;

use App\User;
use Illuminate\Bus\Queueable;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Contracts\Queue\ShouldQueue;

class Welcome extends Mailable
{
    use Queueable, SerializesModels;

    /**
     * With Mailable descendents, any public property is available to view().
     *
     * Or you could pass them manually.
     *
     * @var User
     *
     * @see Mailable::buildViewData()
     */
    public $user;

    /**
     * Create a new message instance.
     */
    public function __construct(User $user)
    {
        $this->user = $user;
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        return $this->view('emails.welcome')
            // Not needed because $this->user is public.
            // ->with(['user' => $this->user])
            ;
    }
}