无法在Laravel中实现“一对多”关系

// User.php
namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

// Post.php
namespace App;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

php artisan make:migration create_posts_table --create=posts

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

class CreatePostsTable extends Migration
{
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->foreignId('user_id')->constrained();
            // 其他字段...
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::dropIfExists('posts');
    }
}

$user = User::find(1);
$posts = $user->posts;

// 创建一个帖子并关联到用户
$user = User::find(1);
$post = new Post(['title' => 'New Post']);
$user->posts()->save($post);

// 更新关联模型
$post = Post::find(1);
$post->user()->associate($user);
$post->save();

// 删除关联模型
$post = Post::find(1);
$post->user()->dissociate();
$post->save();