4 New Simplifications from Dart Web UI

The Dart Web Components package has been renamed to Dart Web UI to better reflect the wide range of functionality found in the library. Also, syntax has been simplified based on feedback from users. This post covers some of the new features and gives tips on how you can migrate your code.

A frost covered spider's web.

Dart Web UI provides polyfills and compilers for Web Components (making them available to today's browsers), dynamic templates, and live data binding inspired by Model Driven Views. You can use Dart Web UI to build modern client-side web apps. For more information, read my blog posts about Dart Web UI or study the detailed article on the subject.

Shorter package names

Old: package:web_components/web_components.dart

New: package:web_ui/web_ui.dart

Your pubspec.yaml now looks like this:

 dependencies:  
  web_ui: any

Simpler two-way data binding for input fields

Old: data-bind="attribute:dartAssignableValue"

New: bind-attribute="dartAssignableValue"

For example:

 <input type="text" bind-value="superlative" placeholder="Enter superlative">

Simpler declarative event handlers

Old: data-action="click:handleClick"

New: on-click="handleClick()"

Notice how the on-action form declares an expression (complete with parentheses). You can pass the event to the handler by using handleClick($event).

For example:

 <select name="language" on-change="chooseExample($event)">  
  <option value="">-- Choose one --</option>  
  <option value="js">JavaScript</option>  
  <option value="java">Java</option>  
 </select>

Simpler conditional templates

Old: <template instantiate="if securityClearance == 'top'">

New: <template if="securityClearance == 'top'">

For example:

 <template if="langChoice != null && !langChoice.isEmpty">  
  <div>  
   <h3>{{ langChoice }}</h3>  
   <code><pre>{{ example }}</pre></code>  
  </div>  
 </template>

Template tag no longer required

Option A: <template if="securityClearance == 'top'">

Option B: <div template if="securityClearance == 'top'">

For example:

 <div template if="langChoice != null && !langChoice.isEmpty">  
  <h3>{{ langChoice }}</h3>  
  <code><pre>{{ example }}</pre></code>  
 </div>

Summary

The Dart Web Components package is now the Dart Web UI package. The name was changed to better reflect the breadth of features available, including polyfills for Web Components, dynamic templates, and live data binding. Recent feedback has helped to simplify some of the syntax around event handlers, conditional templates, and more.

You can discuss Dart Web UI at web-ui@dartlang.org mailing list, or ask questions on Stack Overflow. You can follow the open source Dart Web UI project on Github.

(Picture courtesy of http://www.flickr.com/photos/foxypar4/2124673642/)

Popular posts from this blog

Lists and arrays in Dart

(This is Part 3 in a series about Dart. Check out Part 2, Function in Dart .) Warning : We expect the Dart libraries to undergo potentially sweeping changes before Dart goes to alpha. This document is relevant as of 2011-12-22. Intro Dart is a "batteries included" effort to help app developers build modern web apps. An important "battery" is the bundled core Dart libraries, providing common and rich functionality. Dart is building a solution for large, complex web apps, and providing well tested, integrated, and common libraries is key to helping a web app developer be more productive out of the box. The Collection libraries are a crucial set of APIs that Dart developers get for free. Much more than simple arrays and maps, the Collection library includes standard ways to filter, iterate, inspect, compose, and sort your data. This post specifically looks at List<E> , Dart's ordered, indexable collection of objects. Aside: The Dart project is lucky
Read more

Converting Array to List in Scala

Now, this has to have a built-in somewhere in Scala , because it just seems too common. So, how to convert an Array to a List in Scala? Why do I need this? I needed to drop to Java for some functionality, which in this case returns an Array. I wanted to get that Array into a List to practice my functional programming skillz. **Update**: I figured out how to convert Arrays to Lists the Scala way. Turns out it's a piece of cake. val myList = List.fromArray(Array("one", "two", "three")) or val myList = Array("one","two","three").elements.toList The call to elements returns an Iterator , and from there you can convert to a List via toList . Nice. Because my first version wasn't actually tail recursive, what follows is a true tail recursive solution, if I were to implement this by hand. The above, built in mechanism is much better, though. object ArrayUtil { def toList[a](array: Array[a]): List[a] = { d
Read more

Null-aware operators in Dart

Image
Three new language features just landed in the latest dev channel build of the Dart ! Collectively known as null-aware operators , these new features will help you reduce the code required to work with potentially null objects. I'm excited for these new abilities, because typing less is always a good thing. Read on to learn more, and be sure to try these new features on Dart Pad . ?? Use ?? when you want to evaluate and return an expression IFF another expression resolves to null. exp ?? otherExp is similar to ((x) => x == null ? otherExp : x)(exp) ??= Use ??= when you want to assign a value to an object IFF that object is null. Otherwise, return the object. obj ??= value is similar to ((x) => x == null ? obj = value : x)(obj) ?. Use ?. when you want to call a method/getter on an object IFF that object is not null (otherwise, return null). obj?.method() is similar to ((x) => x == null ? null : x.method())(obj) Yo
Read more