Discover Dart - Meetup 15/02/2017

DISCOVER DART(LANG)
STÉPHANE ESTE-GRACIAS - 15/02/2017

DISCOVER DART(LANG)
THANKS TO
NYUKO.LU REYER.IO

DISCOVER DART(LANG) - INTRODUCTION
DART LANGUAGE: ORIGINS
▸ Open Source Software under a BSD license
▸ Starting in October 2011
▸ Originally developed by Google
▸ Approved as a standard by Ecma in June 2014: ECMA-408
▸ Designed by Lars Bak and Kasper Lund
▸ Legacy developers of V8 Javascript Engine used in Chrome

DART LANGUAGE: INFLUENCES
▸ Syntax: Javascript, Java, C#
▸ Object Model: Smalltalk
▸ Optional Types: Strongtalk
▸ Isolates: Erlang
▸ Compilation Strategy: Dart itself
▸ Dart sounds familiar to “mainstream” developers

DART LANGUAGE: PURPOSES
▸ General-purpose and multi-platform programming language
▸ Easy to learn
▸ Easy to scale
▸ Deployable everywhere
▸ Web (Angular Dart), Mobile (Flutter), Server (VM)
▸ Command Line, IoT…

DART LANGUAGE: ON PRODUCTION
▸ Google depends on Dart to make very large applications
▸ AdWords, AdSense, Internal CRM, Google Fiber…
▸ Over 2 million lines of production Dart code 
Apps can reach hundreds of thousands of lines of code
▸ ReyeR has developed with Dart for 4 years now
▸ BikeMike.Mobi, Daanuu

DART’S NOT JUST A LANGUAGE
▸ Well-crafted core libraries
▸ pub: a Package Manager
▸ Packages are available at pub.dartlang.org
▸ dartanalyzer: a static Analysis Tool for real-time analysis and code completion
▸ dartfmt: a source code reformatter for common coding conventions
▸ dartdoc: generate HTML documentation (triple slashes comments (///))
▸ dartium: a Web browser with Dart included (based on Chromium)
▸ …Unit test, Code Coverage, Proﬁling….

DISCOVER DART(LANG) - LANGUAGE
HELLO WORLD
void main() { 
for (int i = 0; i < 5; i++) { 
print('hello ${i + 1}'); 
} 
} 
$ dart hello_world.dart
hello 1
hello 2
hello 3
hello 4
hello 5

KEYWORDS
▸ class abstract final static implements extends with
▸ new factory get set this super operator
▸ null false true void const var dynamic typedef enum
▸ if else switch case do for in while assert
▸ return break continue
▸ try catch finally throw rethrow
▸ library part import export deferred default external
▸ async async* await yield sync* yield*

OPERATORS
▸ expr++ expr-- -expr !expr ~expr ++expr --expr
▸ () [] . ?. ..
▸ * / % ~/ + - << >> & ^ |
▸ >= > <= < as is is! == != && || ??
▸ expr1 ? expr2 : expr3
▸ = *= /= ~/= %= += -= <<= >>= &= ^= |= ??=

IMPORTANT CONCEPTS
▸ Everything is an object
▸ Even numbers, booleans, functions and null are objects
▸ Every object is an instance of a class that inherit from Object
▸ Everything is nullable
▸ null is the default value of every uninitialised object
▸ Static types are recommended for static checking by tools, but it’s optional
▸ If an identiﬁer starts with an underscore (_), it’s private to its library

VARIABLES
var name = 'Bob'; 
var number = 42; 
 
int number; 
String string; 
int number = 42; 
String name = 'Bob';

FUNCTION: FAT ARROW
bool isNoble(int number) { 
return _nobleGases[number] != null; 
}
bool isNoble(int number) => _nobleGases[number] != null
=> expr syntax is a shorthand for { return expr; }

FUNCTION: OPTIONAL NAMED PARAMETERS
enableFlags({bool bold, bool hidden}) { 
// ... 
} 
 
enableFlags(bold: true, hidden: false);

FUNCTION: OPTIONAL POSITIONAL PARAMETERS
String say(String from, String msg, [String device]) { 
var result = '$from says $msg'; 
if (device != null) { 
result = '$result with a $device'; 
} 
return result; 
} 
 
assert(say('Bob', 'Howdy') == 'Bob says Howdy’);
 
assert(say('Bob', 'Howdy', 'phone') == 'Bob says Howdy with a phone');

CLASS / CONSTRUCTOR / NAMED CONSTRUCTORS
import 'dart:math'; 
 
class Point { 
num x; 
num y; 
 
Point(this.x, this.y);
Point.fromJson(Map json) { 
x = json['x']; 
y = json['y']; 
}
...
... 
 
num distanceTo(Point other) { 
var dx = x - other.x; 
var dy = y - other.y; 
return sqrt(dx * dx + dy * dy); 
} 
}

CASCADE NOTATION
var address = getAddress(); 
address.setStreet(“Elm”, “42”) 
address.city = “Carthage” 
address.state = “Eurasia” 
address.zip(1234, extended: 5678); 
 
getAddress() 
..setStreet(“Elm”, “42”) 
..city = “Carthage” 
..state = “Eurasia” 
..zip(1234, extended: 5678);
result = x ?? value; 
// equivalent to 
result = x == null ? value : x;
x ??= value; 
// equivalent to 
x = x == null ? value : x;
p?.y = 4; 
// equivalent to 
if (p != null) { 
p.y = 4; 
}
NULL AWARE OPERATORS

FUTURE & ASYNCHRONOUS
Future<String> lookUpVersion() async => '1.0.0'; 
 
Future<bool> checkVersion() async { 
var version = await lookUpVersion(); 
return version == expected; 
}
 
 
try { 
server = await HttpServer.bind(InternetAddress.LOOPBACK_IP_V4, 4044); 
} catch (e) { 
// React to inability to bind to the port... 
}

DISCOVER DART(LANG) - GETTING STARTED
TRY DART ONLINE
▸ Online with DartPad https://dartpad.dartlang.org/ 
Supports only a few core libraries

DISCOVER DART(LANG) - GETTING STARTED
INSTALL DART ON YOUR FAVORITE PLATFORM
▸ Install Dart on MacOS, Linux Ubuntu/Debian, Windows
▸ Install an IDE
▸ Recommended: WebStorm or IntelliJ (for Flutter)
▸ Dart Plugins available for
▸ Atom, Sublime Text 3, Visual Studio Code, Emacs, Vim

DISCOVER DART(LANG) - DART VM
CONSOLE APPLICATION; PUBSPEC.YAML
name: console 
version: 0.0.1 
description: A sample command-line application. 
#author: someone <email@example.com> 
#homepage: https://www.example.com 
 
environment: 
sdk: '>=1.0.0 <2.0.0' 
 
dependencies: 
foo_bar: '>=1.0.0 <2.0.0' 
 
dev_dependencies: 
test: '>=0.12.0 <0.13.0'

CONSOLE APPLICATION; LIB/CONSOLE.DART
int calculate() { 
return 6 * 7; 
}

CONSOLE APPLICATION; BIN/MAIN.DART
import 'package:console/console.dart' as console; 
 
main(List<String> arguments) { 
print('Hello world: ${console.calculate()}!'); 
}
$ dart bin/main.dart
Hello world: 42!

CONSOLE APPLICATION; TEST/CONSOLE_TEST.DART
import 'package:console/console.dart'; 
import 'package:test/test.dart'; 
 
void main() { 
test('calculate', () { 
expect(calculate(), 42); 
}); 
} 
$ pub run test
00:00 +1: All tests passed!

DISCOVER DART(LANG) - DART WEBDEV
SIMPLE WEB APPLICATION: PUBSPEC.YAML
name: 'web' 
version: 0.0.1 
description: An absolute bare-bones web app. 
#author: someone <email@example.com> 
#homepage: https://www.example.com 
 
environment: 
sdk: '>=1.0.0 <2.0.0' 
 
#dependencies: 
# my_dependency: any 
 
dev_dependencies: 
browser: '>=0.10.0 <0.11.0' 
dart_to_js_script_rewriter: '^1.0.1' 
 
transformers: 
- dart_to_js_script_rewriter

SIMPLE WEB APPLICATION: INDEX.HTML
<!DOCTYPE html> 
<html>
<head> 
...
<title>web</title> 
<link rel="stylesheet" href="styles.css"> 
<script defer src=“main.dart"
type=“application/dart">
</script> 
<script defer src=“packages/browser/dart.js">
</script> 
</head> 
<body> 
<div id="output"></div> 
</body>
</html>

SIMPLE WEB APPLICATION: STYLES.CSS
@import url(https://fonts.googleapis.com/css?
family=Roboto); 
 
html, body { 
width: 100%; 
height: 100%; 
margin: 0; 
padding: 0; 
font-family: 'Roboto', sans-serif; 
}

SIMPLE WEB APPLICATION: MAIN.DART
import 'dart:html'; 
 
void main() { 
querySelector(‘#output')
.text = 'Your Dart app is running.'; 
}

DISCOVER DART(LANG) - COMMUNITY
EVENTS
▸ Dart Events 
https://events.dartlang.org
▸ Dart Developper Summit 
https://events.dartlang.org/2016/summit/ 
https://www.youtube.com/playlist?list=PLOU2XLYxmsILKY-
A1kq4eHMcku3GMAyp2
▸ Meetup Luxembourg Dart Lang 
https://www.meetup.com/Luxembourg-Dart-Lang-Meetup/

DISCOVER DART(LANG) - COMMUNITY
USEFUL LINKS
▸ Dart lang website https://www.dartlang.org
▸ Questions on StackOverﬂow http://stackoverﬂow.com/tags/dart
▸ Chat on Gitter https://gitter.im/dart-lang
▸ Learn from experts https://dart.academy/
▸ Source code on Github https://github.com/dart-lang

Discover Dart - Meetup 15/02/2017

Discover Dart - Meetup 15/02/2017

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Discover Dart - Meetup 15/02/2017