Call to a member function update() on null in laravel 9 - laravel-8

Question

What is wrong with this function? I ve got error on this line:
$bookShelf->update($request->all());
My Controller
<?php
namespace App\Http\Controllers;
use App\Models\BookShelf;
use App\Models\Book;
use App\Models\Category;
use App\Http\Requests\StoreBookShelfRequest;
use App\Http\Requests\UpdateBookShelfRequest;
class BookShelfController extends Controller
{
/**
* Display a listing of the resource.
*
* #return \Illuminate\Http\Response
*/
public function index()
{
$bookshelves = BookShelf::with('book')->latest()->get();
// $bookshelves = BookShelf::all();
$model = new BookShelf();
$books = Book::with('category')->latest()->get();
// $books = Book::all();
$categories = Category::with(['users.books.shelf']);
return view('admin.bookshelves.index', compact('bookshelves', 'books', 'model', 'categories'));
}
/**
* Show the form for creating a new resource.
*
* #return \Illuminate\Http\Response
*/
public function create()
{
$model = new BookShelf;
$categories = Category::all();
$books = Book::with('category')->latest()->get();
return view('admin.bookshelves.create', compact('categories', 'model', 'books'));
}
/**
* Store a newly created resource in storage.
*
* #param \App\Http\Requests\StoreBookShelfRequest $request
* #return \Illuminate\Http\Response
*/
public function store(StoreBookShelfRequest $request)
{
BookShelf::create($request->all());
return redirect('admin_area/shelves')->with('success', 'Selamat Data Berhasil Ditambahkan');
}
/**
* Display the specified resource.
*
* #param \App\Models\BookShelf $bookShelf
* #return \Illuminate\Http\Response
*/
public function show(BookShelf $bookShelf)
{
//
}
/**
* Show the form for editing the specified resource.
*
* #param \App\Models\BookShelf $bookShelf
* #return \Illuminate\Http\Response
*/
public function edit($shelf_code)
{
$model = BookShelf::find($shelf_code);
$categories = Category::all();
$books = Book::with('category')->latest()->get();
return view('admin.bookshelves.edit', compact('categories', 'model', 'books'));
}
/**
* Update the specified resource in storage.
*
* #param \App\Http\Requests\UpdateBookShelfRequest $request
* #param \App\Models\BookShelf $bookShelf
* #return \Illuminate\Http\Response
*/
public function update(UpdateBookShelfRequest $request, BookShelf $bookShelf)
{
$bookShelf = BookShelf::find($bookShelf->shelfcode);
$bookShelf->update($request->all());
return redirect('admin_area/bookshelves')->with('success', 'Selamat Data Berhasil Di Ubah');
}
/**
* Remove the specified resource from storage.
*
* #param \App\Models\BookShelf $bookShelf
* #return \Illuminate\Http\Response
*/
public function destroy(BookShelf $bookShelf, $id)
{
$bookShelf = BookShelf::find($id);
$bookShelf->delete();
return redirect('admin_area/shelves')->with('success', "Data berhasil disimpan");
}
}
My Model
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
class BookShelf extends Model
{
use HasFactory;
protected $guarded = ['id'];
protected $load = ['category', 'book'];
public function category()
{
return $this->belongsTo(Category::class);
}
public function book()
{
return $this->belongsTo(Book::class);
}
public function getRouteKeyName()
{
return 'shelfcode';
}
}
My Edit View
#extends('layouts.main')
#section('title', 'Edit Data Buku')
#section('content')
<div class="container">
<div class="row mt-3 d-flex justify-content-center">
<div class="col-md-9 justify-content-center">
<div class="card card-primary card-outline">
<div class="card-header">
<h5 class="m-0">Edit Data Rak Buku</h5>
</div>
<div class="card-body">
<h6 class="card-title"></h6>
<form method="POST" action="{{ route('shelves.update', $model->shelfcode) }}"
enctype="multipart/form-data">
#csrf
{{-- <input type="hidden" name="_method" value="PATCH"> --}}
#method('PUT')
#include('admin.bookshelves.form')
<div class="form-group">
<button class="btn btn-warning btn-sm glyphicon glyphicon-save">
<span class="fas fa-edit"> Edit Data Buku</span>
</button>
</div>
</form>
{{-- #endsection --}}
</div>
</div>
</div>
</div>
</div>
#endsection

Answer 1

Looks like you're querying your BookShelf model by the wrong key. You can also remove $bookShelf = BookShelf::find($bookShelf->shelfcode); from the update function since it is already injected by the framework when you use model binding (https://laravel.com/docs/9.x/routing#route-model-binding).

Answer 2

When you have this common error, there is no trap, it litteraly means that you are trying to call update on null.
It's exactly like doing null->update($request->all()) (and you can try, you'll have the same error).
The only explanation here is that $bookShelf = BookShelf::find($bookShelf->shelfcode); returns null.
Regarding the structure itself,
public function update(UpdateBookShelfRequest $request, BookShelf $bookShelf)
{
$bookShelf = BookShelf::find($bookShelf->shelfcode);
//...
}
makes no sense since the whole purpose of using implicit route binding is to avoid the manual query you are making to retrieve $bookShelf. It should already be the BookShelf you need.