Pin

If Flask for Python is a micro web app framework, then Pin is a pico framework.

Pin is written in pure Dart and allows you to create REST APIs and other web apps using a simple syntax that uses annotations.

Usage

The most simple example of an app using Pin looks like this:

import 'package:pin/pin.dart';
import 'dart:io';

@Route('/')
class BaseRoute extends RouteController {
  @override
  void get(HttpRequest req, Context context, Map<String, String> params) {
    req.response.write('Hello world!');
  }
}

void main() async {
  var app = App();
  app.addRoute(BaseRoute);
  await app.start();
}

Note that there is no need to call flush or close on the HttpRequest's HttpResponse. Pin will do this for you.

This can then be queried by a client by subsequently running this:

import 'dart:convert';
import 'dart:io';

void main() async {
  var client = HttpClient();
  var request = await client.get('localhost', 8080, '/');
  var response = await request.close();
  print(await response.transform(utf8.decoder).join());
}

A More Complex Example

See example/pin_example.dart to see how to use path parameters, and add services to the app.

How does it work?

Pin uses Dart's mirrors API examine the classes you passed into app.addRoute and checks for three conditions:

1. A valid Route annotation
2. That the class inherits from RouteController
3. That the class has a no args constructor

If these conditions are not met, the app will terminate immediately with a (hopefully) informative exception.

When a route is called by a client, the app will then instantiate a corresponding class to respond to that client's query.

Other

I made Pin in order to better understand how HTTP and web app frameworks work. If you spot a bug, need some help, or want a feature added, drop a comment and let me know. Pull requests welcome.