DART

for

HIPSTERs







dominik.wronski@gmail.com







      @DominikWro


AGENDA


What is DART


Why it's cool


MV* APP

What is DART

Short answer:

                                              javascript Google way

Longer (technical) answer:

Purely Object-Oriented, optionally typed, class-based, single inheritance with actor-based concurrency language.

Hello World

// Define a function. 
printHello(String aword) { 
  print('Hello $aword!'); 
}
 
// This is where the app starts executing. 
main() { 
  var word = "world"; 
  printHello(word);  
}

Hello World

AGAIN :)


// simple web server
runServer(String basePath) {
  HttpServer server = new HttpServer();
  server.defaultRequestHandler = new StaticFileHandler(basePath).onRequest;
  server.listen('127.0.0.1', 1337);
}

main() {
  File script = new File(new Options().script);
  script.directory().then((Directory d) {
    runServer(d.path);
  });
}


DARTIUM


dart2js




GOALS


PERFORMANCE


BIG WEBSITES


NICE TO WORK WITH

PERFORMANCE

amazon.com    600 kb

cnn.com            1.5 mb 

https://www.dartlang.org/performance/


Why dart is faster


simpler object model

programs are declared not constructed at a runtime

fewer special corner cases

DART VM 

Sophisticade hacks 
(i.e. tree shaking)

Biger Websites

Source: Google I/O 2013 https://www.dartlang.org/slides/

Solution


core libraries

  • dart: core

  • dart: async

  • dart: html

  • dart: io

  • ...


Languages features 


or

 
why it's nice to write in dart

  • Good core library

  • Syntax

  • Futures

  • Streames

  • Mixins

  • Isolates



CORE Libraries


Dart:html


// No jQuery:
var elements = document.querySelectorAll('slide');
for(int i = 0 ; i < elements.length; i++) { 
  elements[i].class Name = element.className + 'swing'; 
}

// jQuery:
$('slide').addClass('swing');

// Dart 
queryAll('slide').classes.add('swing')


Syntax

Optionaly typed

multiply(num x, num factor) {
  return x * factor;
}

main() {
  print( multiply(4, "hello") ); // WARNING at this line, string isn't assignable to number


Double and Integer

Integers are faster

Futures


catService.getCatData("cute", (cat) {                //js
  catService.getCatPic(cat.ImageId, (pic) {
    imageWorker.rotate(pic, 30, (rotated) {
      draw(rotated);
    });
  });
}); 

catService.getCat("cute")                            //dart
 .then((cat) => catService.getCatPicture(cat.ImageId))
 .then((pic) => imageWorker.rotate(pic, 30)) 
 .then((rotated) => draw(rotated))

Streams

import 'dart:async';

main() {

// Some code  >> Don't need to read this comments <<
// I already told you there is no need to read this comment

  var subscription = stream.listen(null); 
  subscription.onData((value) { 
    print("listen: $value"); 
  if (value == 2) subscription.cancel(); // cancel the subscription 
  }); 
  subscription.onError((err) => print("error: $err"));     
  subscription.onDone(() => print("done"));
}

MIXINS 

abstract class Persistence {     
void save(String filename) {    
  print('saving the object as ${toJson()}');     
  }         
void load(String filename) {      
    print('loading from $filename');     
  }         
   Object toJson();    
}abstract class Warrior extends Object with Persistence {          
  fight(Warrior other) {      
       // ...     
   }    
}        

class Ninja extends Warrior {     
  Map toJson() {      
    return {'throwing_stars': true};     
    }    
  }        

class Zombie extends Warrior {     
  Map toJson() {      
    return {'eats_brains': true};     
    }    
  }

Isolates

  • Isolated memory heap
  • Actor-based concurrency
  • Each isolate is conceptually a process
  • Nothing shared, all communication via message passing
  • Compile to webworkers for HTML5
  • Inspired by Erlang processes
import 'dart:isolate'; 

longRunningCalculation() { 
  port.receive((msg, replyTo) { 
if (msg == 'go') { 
// do long calculation 
      replyTo.send(result); 
    } 
  }); 
}

main() { 
  SendPort sendPort = spawnFunction(longRunningCalculation);     
  SendPort.call('go').then((result) => print('Result is $result')); 
// continue to respond to input events while long calculation is running 
}


backbone.js style MV* app



OUR_APP/                     
                     app.dart
                    
                     /WEB
                                          index.html
                                          main.dart
                                          style.css
                      /LIB
                                          Models.ComicBook.dart
                                          Collections.Comics.dart    
                                          Views.AddComic.dart
                                          Views. AddComicForm.dart
                                          Views.Comics.dart
                                          ModalDialog.dart

                                 

index.html

<!DOCTYPE html>
<html>
<head>
  <title>Dart Comics</title>

  <link rel="stylesheet" href="/stylesheets/style.css">


  <script src="packages/browser/dart.js"></script>

  <script src="main.dart" type="application/dart"></script>

</head>

<body>
  <h1>Dart Comics</h1>

  <p>Welcome to Dart Comics</p>


  <ul id="comics-list"></ul>


  <p id="add-comic">Add a sweet comic to the collection.</p>

</body>
</html>

import 'dart:io';                              // app.dart


import 'package:json/json.dart' as JSON;


import 'package:dirty/dirty.dart';


import 'package:uuid/uuid.dart';


import 'package:ansicolor/ansicolor.dart';


main() {

  var port = Platform.environment['PORT'] == null ?

    8000 : int.parse(Platform.environment['PORT']);

    HttpServer.bind('127.0.0.1', port).then((app) {

    //app.listen(Public.matcher, Public.handler);

    app.listen((req) {

      log(req)

      if (req.method == 'GET' && req.uri.path == '/comics') {

        return Comics.index(req);  }

      if (req.method == 'POST' && req.uri.path == '/comics') {

        return Comics.post(req);}

      if (req.method == 'DELETE' &&

          new RegExp(r"^/comics/[-\w\d]+$").hasMatch(req.uri.path)) {

        return Comics.delete(req);}

      if (Public.matcher(req)) {

        return Public.handler(req); }

      HttpResponse res = req.response;

      res.statusCode = HttpStatus.NOT_FOUND;

      res.write("Not found.");

      res.close();

    });

    print('Server started on port: ${port}');

  });


}




class Comics {                                       //app.dart

  static Uuid uuid = new Uuid();

  static Dirty db = new Dirty('dart_comics.db');


  static index(HttpRequest req) {

    // print(db.values.toList());

    HttpResponse res = req.response;

    res.headers.contentType

      = new ContentType("application", "json", charset: "utf-8");


    res.write(JSON.stringify(db.values.toList()));

    res.close();

  }
static post(HttpRequest req) {
  ...
  }
static delete(HttpRequest req) {
  ...
  }

main.dart

import 'package:dart_comics/Collections.Comics.dart' as Collections;


import 'package:dart_comics/Views.Comics.dart' as Views;


import 'package:dart_comics/Views.AddComic.dart' as Views;
import 'dart:html';


import 'package:json/json.dart' as JSON;


import 'package:hipster_mvc/hipster_sync.dart';



main() {

  // HipsterSync.sync = localSync;

  var my_comics_collection = new Collections.Comics(),

      comics_view = new Views.Comics(

        el:'#comics-list',

        collection: my_comics_collection

      );

  my_comics_collection.fetch();

  new Views.AddComic(

    el:'#add-comic',

    collection: my_comics_collection

  );


}


localSync(method, model) {
  final completer = new Completer();
  print("[local_sync] $method");
  if (method == 'read') {
    var json = window.localStorage[model.url],
        data = (json == null) ? {} : JSON.parse(json);
    completer.complete(data.values);
  }
  if (method == 'create') {
    var collection = model.collection,
        attrs = model.attributes;
    if (attrs['id'] == null) {
      attrs['id'] = "${attrs['title']}:::${attrs['author']}".hashCode;
    }
    print(attrs);

collection.create(attrs);
    var id = attrs['id'];
    collection.data[id] = attrs;
    window.localStorage[collection.url]= JSON.stringify(collection.data);
  }
  return completer.future;
}


try.dartlang.com




http://www.google.com/elections/

Dart SDK 1.0 released 14 Nov 2013



Made with Slides.com