问缺少文件下载路由所需的参数

EN

 Route::get('download/{mixtape_file}', 'MixtapeController@download')-
    >name('download');

 <a href="{{ route('download', $mixtape->mixtape_file) }}">
    <button class="btn btn-primary">Download</button>
 </a>

 public function download($mixtape_file)
 {
    $mixtape = Mixtape::where('mixtape_file', '=', $mixtape_file)-
    >firstOrFail();
    $file = public_path('audio/' . $mixtape->mixtape_file);

    return response()->download($file);
 }