在Laravel中检查重复数据

use Illuminate\Support\Facades\DB;

// 检查用户名是否已存在
$username = 'exampleUser';
$isDuplicate = DB::table('users')->where('username', $username)->exists();

if ($isDuplicate) {
    // 用户名已存在
} else {
    // 用户名可用
}

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    protected $fillable = ['username', 'email'];

    public function scopeUniqueUsername($query, $username)
    {
        return $query->where('username', $username)->first();
    }
}

use App\Models\User;

$username = 'exampleUser';
$user = User::uniqueUsername($username);

if ($user) {
    // 用户名已存在
} else {
    // 用户名可用
}

namespace App\Listeners;

use App\Events\UserCreating;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Queue\InteractsWithQueue;

class CheckDuplicateUser implements ShouldQueue
{
    public function handle(UserCreating $event)
    {
        $user = $event->user;
        if (User::where('username', $user->username)->exists()) {
            throw new \Exception('用户名已存在');
        }
    }
}

protected $listen = [
    UserCreating::class => [
        CheckDuplicateUser::class,
    ],
];