Dart examples

This site is an example of different features of the Dart language. I put it together as an excercise while learning Dart. Dart is not only a languge, it's a platform and developement tool-chain. Partially the next evolutionary stage of Google Web Toolkit (GWT), Dart is also meant an ambitious replacement for JavaScript, the standing Web programming langauge.

All pages including the home include all kind of features and effects implemented in Dart. To name few: Hiding sections enhancing usability, animations dramatizing algorithm inner working and simple toys and easter eggs. The point of this site is to explore dart and all it's features. Additionally, the code is meant to be read much as examples are. The code should is written in a particular style, noticable hrough the axamples.

• Levenstein distance calculator
• Dijkstra's shortest path algoritm

TODOs:

• Bar display Polymer demo

Notes:

Dart syntax

#symbols

Symbol class is similar to symbols in Ruby. The syntax allows for ad-hoc enumaration, which does not suffer from non-extendibility like Java's enums

function(can, have, {optional, arguments : withDefaulValue}

Enclose optional function arguments into brackets, default value may follow after a colon.

static Named.constructors()

Static functions are also named constructors. Calls to them are prepended with new keyword. The resulting value is a new object as if using a constructor

Constructior(a, b) : initializers = a, list = b { /*...*/ }

Final fields have to be initialized before constructor body executes. This is achieved using constructor initialize, which are put after semicolon just before constructor body.

@Annotations

Dart has annotations with syntax similar to Java annotations.

Dart API

Dart has no arrays

There is Iterable class, Collection extends it. Set, List and Queue

List<T> methods throws RangeError

Use add() method to add elements. A list can be indexed only for reading or setting items, not to add new items.

Unit testing framework

For writing unit tests, there is the unittest package, which can be put into dev_dependencies in pubspec.yaml file. Tests are defined using the test() method taking test name and test function as parameter. The test() methods are called from main() function and for browser apps the test script is included into a blank html page, which will be filled with test results.

Expectation matchers

Expectations in tests are modelled similarly to hamcrest matchers in Java. There's plenty of expectation matchers.

Test PASS, FAIL and ERROR

A test can PASS, or FAIL the expectations. Alternativelly, if an exception is thrown during test execution, the test can result in ERROR.

Dart libraries

Polymer - reusable HTML components

Polymer is a dart library, which allows to create custom HTML tags, with login and markup isolated fromthe rest of application. Polymer needs to be imported into HTML page and initialized. The HTML page then can import and reference custom tags. A custom tag has <template< and <script<.

Polymer - <template> tag

Template tag in a polymner component HTML can include a style tag and arbitrary HTML tags, whch create the component visual appearence.

Polymer - template {{expression}}

Template tag in a polymner component HTML can include a <style< tag and arbitrary HTML tags, whch create the component visual appearence.

Polymer - declarative on-event="" handlers

<template> tag in a polymner component HTML can include a style tag and arbitrary HTML tags, whch create the component visual appearence.

Polymer - script

The script defines a class annotated with @CustomTag. The annotation takes element name as option. The class may extend PolymentElement class, override it's methods and provide new methods and behaviour to the component.

$['selector'] instead of querySelector()

Use $['selector'] to access component DOM