Method App\Http\Controllers\Auth\RegisterController::validator does not exist

I am trying to do registration of multi-user in my registration controller and used the following code and checked. But it shows me error:

Method App\Http\Controllers\Auth\RegisterController::validator does not exist.

<?php

namespace App\Http\Controllers\Auth;

use App\Admin;
use App\Manager;
use App\Http\Controllers\Controller;
use Illuminate\Support\Facades\Hash;
use Illuminate\Support\Facades\Validator;
use Illuminate\Foundation\Auth\RegistersUsers;
use Illuminate\Foundation\Validation\ValidatesRequests;
use Illuminate\Http\Request;


class RegisterController extends Controller
{
    use RegistersUsers;

    public function __construct()
    {
        $this->middleware('guest');
        $this->middleware('guest:admin');
        $this->middleware('guest:manager');
    }

    protected function createAdmin(Request $request)
    {
        $this->validator($request->all())->validate();
        $admin = Admin::create([
            'name' => $request['name'],
            'email' => $request['email'],
            'password' => Hash::make($request['password']),
        ]);
        return redirect()->intended('login/admin');
    }

    protected function createManager(Request $request)
    {
        $this->validator($request->all())->validate();
        $manager = Manager::create([
            'name' => $request['name'],
            'email' => $request['email'],
            'password' => Hash::make($request['password']),
        ]);
        return redirect()->intended('login/manager');
    }
}

via Chebli Mohamed