嗨,我是新来的laravel,在理解如何建立关系方面有些挣扎。我正在尝试在laravel中创建一个基本的Restful API,并具有3个模型
class Book extends Model {
public function author()
{
return $this->belongsTo(Author::class);
}
public function categories()
{
return $this->belongsToMany('App\Category', 'category_book')
->withTimestamps();
}
}
class Author extends Model
{
public function books(){
return $this->hasMany(Book::class);
}
}
class Category extends Model
{
public function books()
{
return $this->belongsToMany('App\Book', 'category_book')
->withTimestamps();
}
}
表迁移:
Schema::create('books', function (Blueprint $table) {
$table->engine = "InnoDB";
$table->increments('id');
$table->string('ISBN', 32);
$table->string('title');
$table->integer('author_id')->unsigned();
$table->float('price')->default(0);
$table->timestamps();
});
Schema::create('authors', function (Blueprint $table) {
$table->engine = "InnoDB";
$table->bigIncrements('id');
$table->string('name');
$table->string('surname');
$table->timestamps();
});
Schema::create('categories', function (Blueprint $table) {
$table->engine = "InnoDB";
$table->bigIncrements('id');
$table->string('name');
$table->timestamps();
});
Schema::create('category_book', function (Blueprint $table) {
$table->bigIncrements('id');
$table->integer('category_id')->unsigned();
//$table->foreign('category_id')->references('id')->on('categories')->onDelete('cascade');
$table->integer('book_id')->unsigned();
//$table->foreign('book_id')->references('id')->on('books')->onDelete('cascade');
$table->timestamps();
});
books是主要的表格,作者与书籍具有一对多的关系。类别与书籍有很多关系,因为一本书可以属于多个类别。
books表具有一个author_id字段,可将其链接到作者的表。还有一个名为category_books的数据透视表,其中包含category_id和book_id,用于将书籍链接到类别。
说我想创建一个新的书记录,如果作者存在以将该书与该作者相关联,但如果不存在,我想创建一个新的作者记录,然后将该书与该作者相关联?
我也希望能够对类别执行相同的操作
我的bookscontroller中具有以下内容:
public function store(Request $request)
{
$book = new book;
$book->title = $request->title;
$book->ISBN = $request->ISBN;
$book->price = $request->price;
$book->categories()->associate($request->category);
$book->save();
return response()->json($book, 201);
}
答案 0 :(得分:1)
首先,在一行中
$book->categories()->associate($request->category);
要更新associate()
关系时使用方法belongsTo
。
$ book-> categories()是多对多关系(belongsToMany
),因此应改用attach()
。
第二,如果要关联可能存在或不存在的作者,则可以使用firstOrCreate
方法。
$author = Author::firstOrCreate([
'name' => $request->author_name,
'surname' => $request->author_surname
]);
$book->author()->associate($author);
您可以针对“类别”或“图书”执行相同的操作。
$category = Category::firstOrCreate([
'name' => $request->category_name
]);
$book->categories()->attach($category);
$book = Book::firstOrCreate([
'ISBN' => $request->book_isbn,
'title' => $request->book_title,
'price' => $request->book_price
]);
$category->books()->attach($book);
此处记录了firstOrCreate()
的使用
https://laravel.com/docs/5.8/eloquent#other-creation-methods
此页面上有更多关于雄辩关系方法的信息
https://laravel.com/docs/5.8/eloquent-relationships