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Showing posts from September, 2013

Forms, HTTP servers, and Polymer with Dart

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(Update of this old Web UI post. Updated as of Jan 17, 2014 and Dart 1.1.)

Dart can be used on the client and the server. This post shows how to:

build a form as a custom elementbind input fields to a Dart objectbuild a Dart HTTP serverhandle and parse a form submit

For lots more Polymer.dart examples, be sure to check out the Dart Polymer Samples. You can find the code for this post at my Github account. Step 1: Install the packages Open up pubspec.yaml (used by the pub package manager) and add the dependencies for Polymer.dart and http_server.
name: parse_form_submit description: A sample Polymer application dependencies: polymer: any http_server: any
Source for pubspec.yaml. Step 2: Create the model class This class is for the "business object". It is bound to the form, so we make its fields observable.
library models; import 'package:polymer/polymer.dart'; class Person extends Object with Observable { @observable String firstName; @observable String lastNa…

JavaZone Report. Spoiler: Awesome.

I had the pleasure of presenting Dart and Web Components at JavaZone 2013 in Oslo, Norway, and I'm so very happy I had the chance. The audience was clearly interested in Dart, the organizers are truly professional and welcoming, the crowd was friendly, the A/V setup was top-notch, and the logistics were easy.

JavaZone is produced by JavaBin, a large network of Java user groups across Norway. I believe this was the 12th or 13th year for JavaZone. The conference has the feel of a big happy meetup. It's chill, mostly local attendees, mostly local vendors (though I did see JetBrains and Atlassian), and approximately 2000 attendees. Don't let "meetup" fool you, this is a full conference: two days, seven concurrent tracks, professional A/V, swag, food, etc. I liked how this was a conference built by the fans, for the fans.

There is continuous food during the conference. You will never go hungry during JavaZone. There was also a coffee bar serving individual drop coffee…

You complete me, unless you already have a Dart future

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Dart Protip: if you already have an instance of Future, you probably don't need a Completer. Simply return the last Future.



If you find yourself using Completers inside of Futures, like this:

// NOT recommended. Future doStuff() { Future future = someAsyncProcess(); Completer completer = new Completer(); future.then((msg) { bool result = msg.result as bool; completer.complete(result); }); return completer.future; }

then I'm happy to report there's a better way. Dart's Futures chain, so you can do this instead:

// Recommend. Future doStuff() { return someAsyncProcess().then((msg) => msg.result); }

The last Future in a chain can return another Future, or simply a value. It's always a good idea to return a Future from a function that uses a Future. This way, the caller knows when the method finished its async work, and can properly handle potential errors.

Completers are great for bridging a callback-based API w…