Solution for "Understanding Reflection in Dart" video tutorial on YouTube

main.dart

import 'dart:io';
import 'dart:mirrors';

main() async {
  var server = await HttpServer.bind('localhost', 8085);

  await for (HttpRequest req in server) {
    // Create InstanceMirror type from which 
    // we retrieve metadata information
    var ref = reflect(Endpoint(req));

    var path = req.uri.path;
    var routeAnnotation = ref.type.metadata
        .firstWhere((meta) => meta.reflectee is Route, orElse: () => null);

    if (routeAnnotation != null && path == (routeAnnotation.reflectee as Route).url) {
      ref.type.instanceMembers.forEach((_, member) {
        // Make initial checks to target the correct members
        if (member.isOperator ||
            !member.isRegularMethod ||
            member.owner.simpleName != #Endpoint) return;

        // Read the @RouteMethod annotations
        var routeMethod = member.metadata.firstWhere(
            (meta) => meta.reflectee is RouteMethod,
            orElse: () => null);
        
        // Match correct @RouteMethod and...
        if (routeMethod != null && (routeMethod.reflectee as RouteMethod).method == req.method) {
          print(member.simpleName);
          
          // ...invoke instance method
          ref.invoke(member.simpleName, []);
        }
      });
    }

    await req.response.close();
  }
}

// Annotations
class Route {
  const Route(this.url);
  final String url;
}

class RouteMethod {
  const RouteMethod(this.method);
  const RouteMethod.get() : this('GET');
  const RouteMethod.post() : this('POST');
  const RouteMethod.put() : this('PUT');
  const RouteMethod.delete() : this('DELETE');

  final String method;
}

// Annotated class
@Route('/')
class Endpoint {
  Endpoint(this._req);

  final HttpRequest _req;

  @RouteMethod.get()
  handleGet() => _req.response.write('Got GET request.');

  @RouteMethod.post()
  handlePost() => _req.response.write('Got POST request.');

  @RouteMethod.put()
  handlePut() => _req.response.write('Got PUT request.');

  @RouteMethod.delete()
  handleDelete() => _req.response.write('Got DELETE request.');
}