我在Laravel中有書籍和作者的多對多關系，需要檢查作者是否已經存在于資料庫中，直到創建和更新書籍

每次我創建新書或使用同一作者更新時，同一作者的新實體都會在 db 中創建

這是我的代碼

這是 BooksController

    <?php

namespace App\Http\Controllers;

use App\Models\Author;
use App\Models\Book;
use Illuminate\Http\Request;

class BooksController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        $books = Book::orderBy('created_at', 'desc')->with('authors')->paginate(5);

        return view('books.index', [
            'books' => $books
        ]);
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        return view('books.create');
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        $request->validate([
            'author_name' => 'required',
            'title' => 'required',
            'release_year' => 'required|numeric',
            'status' => 'required',
        ]);
      
      

我想我需要在這里檢查

        //     check if author already exists..
        // $authors = Author::all();
        // foreach($authors as $a){
        //     if($a->name == $request->input('author_name')){
        //         $author = $a;
        //     }else{
                
        //     }
        // }
        

在這里，如果我在資料庫中有 Glukhovski 并使用同一作者創建新書，則資料庫中會添加另一本 Glukhovski，所以我認為必須有一種方法可以檢查作者是否已經存在，通過資料透視表將其分配給這本書？

        $author = Author::create([
            'name' => $request->input('author_name')
        ]);

        $book = Book::create([
            'title' => $request->input('title'),
            'release_year' => $request->input('release_year'),
            'status' => $request->input('status')
        ]);
        
        $book->authors()->attach($author->id);

        return redirect('/books');

    }


    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        $book = Book::find($id);

        return view('books.show')->with('book', $book);
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        $book = Book::find($id);

        return view('books.edit')->with('book', $book);
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        $request->validate([
            'author_name' => 'required',
            'title' => 'required',
            'release_year' => 'required',
            'status' => 'required',
        ]);

還有這里

        // check if author already exists.....


        //

        $author = Author::create([
            'name' => $request->input('author_name')
        ]);

        $book = Book::find($id);

        $book -> update([
            'title' => $request->input('title'),
            'release_year' => $request->input('release_year'),
            'status' => $request->input('status')
        ]);

        $book->authors()->sync($author->id);

        return redirect('/books');
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        Book::find($id)->delete();

        return redirect('books');  
    }
}

資料透視表

    <?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreateAuthorBookTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('author_book', function (Blueprint $table) {
            $table->id();
            $table->foreignId('author_id');
            $table->foreignId('book_id');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('author_book');
    }
}

uj5u.com熱心網友回復：

您可以在創建作者之前通過這種方式首先檢查作者，如果作者不存在，它將創建一個新的

 $author = Author::where('name',$request->input('author_name'))->first();
 if(!$author){
     $author = Author::create([
         'name' => $request->input('author_name')
     ]);
 }
 

標籤：拉拉维尔

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