I can't update the field in laravel 5 - laravel

Question

It is OK in Get, Post, Delete in my laravel code.
But I can't update the field.
function update in BookController.php
$data = $this->request->all();
If show the dd($data), it is null.
What reason?
Help me please.
BookRequest.php Code:
<?php
namespace App\Http\Requests;
use Illuminate\Foundation\Http\FormRequest;
class BookRequest extends FormRequest
{
public function authorize()
{
return true;
}
public function rules()
{
return [
'name' => 'required|max:255',
'coment' => 'required'
];
}
}
BookController.php Code:
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Book;
use Illuminate\Http\Response;
use App\Http\Requests\BookRequest;
class BookController extends Controller
{
protected $request;
protected $book;
public function __construct(Request $request, Book $book) {
$this->request = $request;
$this->book = $book;
}
public function update(BookRequest $request, $id) {
$data = $this->request->all();
$book = $this->book->find($id);
$book->name = $data['name'];
$book->coment = $data['coment'];
$book->save();
return response()->json(['status' => Response::HTTP_OK]);
}
}

Answer 1

If i were you i would replace the Controller like below:
<?php
namespace App\Http\Controllers;
use App\Book;
use Illuminate\Http\Response;
use App\Http\Requests\BookRequest;
class BookController extends Controller
{
public function update(BookRequest $request, $id) {
$book = Book::find($id);
$book->update($request->all());
return response()->json(['status' => Response::HTTP_OK]);
}
}
If you have set up Route:model binding then you can simplify Code more better. Below code only works if you have a Route::model setup in your route file web.php.
Check this docs for more details:
https://laravel.com/docs/5.6/routing#route-model-binding
public function update(BookRequest $request, Book $book) {
$book->update($request->all());
return response()->json(['status' => Response::HTTP_OK]);
}

Answer 2

Try this:-
$request->all();
instead of
$this->request->all()

Answer 3

I have solved.
My request: http://127.0.0.1:8000/api/book
POST , key: _method: PUT
Update Code
$data = $request->all();
$book = Boook::find($id);
$book->name = $data['name'];
$book->coment = $data['coment'];
$book->save();
Regards.