/**
  * Bootstrap any application services.
  *
  * @return void
  */
 public function boot()
 {
     Blade::directive('datetime', function ($expression) {
         return "<?php echo explode(' ', trim({$expression}, '()'))[0]; ?>";
     });
     Blade::directive('filesize', function ($expression) {
         return "<?php echo '[' . round({$expression} / 1024 / 1024, 2) . 'M]'; ?>";
     });
     Album::saved(function () {
         return response()->json('成功上传!');
     });
     Song::saved(function () {
         return response()->json('成功上传!');
     });
 }