Saturday, 17 June 2017

A Multiplicity of Singleton Services

Angular Services are singletons right? Google it and you will get plenty of pages saying they are. Well sometimes they are and sometimes they are not!

I was working on a service that didn't seem to be working. To debug, I put a print statement in the constructor and I received 2 messages. So what's happening? Turns out to be down to Providers

Suppose you have a component and you want to use a service, you may have declared it in each component like this:

providers: const [TextProcessingService]

This actually creates a new instance before injecting it into your component.

So say we only want one instance ever? How do we do it? First step, delete that Providers declaration. Next declare at the bootstrap level:

  bootstrap(
      AppComponent, [TextProcessingService]
  );

Hope this blog post clears up confusion for anyone else. It is actually quite a powerful feature, allowing you to keep services and components totally separate.

Thursday, 15 June 2017

Dart SDK and Dartium 1.24.1 Chocolatey Packages for Windows

Chocolatey is a package manager for Windows similar to Linux's apt-get, based on Microsoft's Nuget tool and Powershell scripting language. It works from the command-line and from a WPF GUI interface.

You can install unmoderated versions by specifiying the install version during installation.
Chocolatey has also been updated with versions 1.24.1
Command line installation:
choco uninstall dart-sdk

choco install -y dart-sdk  -version 1.24.1
To verify you have the right version on your path.
dart --version
Dart VM version: 1.24.1 (Wed Jun 14 07:53:19 2017) on "windows_x64"

Command line installation:
choco uninstall dartium

choco install -y dartium  -version 1.24.1

Tuesday, 13 June 2017

Dart SDK and Dartium 1.24.0 Chocolatey Packages for Windows

Chocolatey is a package manager for Windows similar to Linux's apt-get, based on Microsoft's Nuget tool and Powershell scripting language. It works from the command-line and from a WPF GUI interface.

You can install unmoderated versions by specifiying the install version during installation.
Chocolatey has also been updated with versions 1.24.0
Command line installation:
choco uninstall dart-sdk

choco install -y dart-sdk  -version 1.24.0
To verify you have the right version on your path.
dart --version
Dart VM version: 1.24.0 (Mon Jun 12 08:37:04 2017) on "windows_x64"

Command line installation:
choco uninstall dartium

choco install -y dartium  -version 1.24.0

Tuesday, 30 May 2017

Introducing NB8080 - a simple Notes Board application

Time for a new productivity web app project! This time a notes application with a similar philosophy to NP8080. This means offline, 100% local storage of data, easy to use and a focus on emerging browser features. No Angular this time - just vanilla dart:html.

Enjoy the first version of NB8080.win - feedback would be great!

The app works offline thanks to the excellent PWA package. For details see the article 'Making a Dart web app offline-capable: 3 lines of code'.

NB8080 is on GitHub - star, grab the code and raise issues!

Wednesday, 3 May 2017

Moving To AngularDart 3

Angular Dart 3 final was released and NP8080 (simple web based text editor) has been built with the latest version. It has been a fun little project and I have found myself using it daily as a scratchpad.

Not a massive amount to report - Angular very stable since the Betas. Certainly feeling a bit more Dart-y. The most disruptive change was the deprecation of EventEmitter but as this was a thin wrapper around a standard Dart Stream it wasn't much of a loss though I had 20 occurrences to update!

The code is straightforward as:

  final StreamController onShowDialogChange = new StreamController();
  ...
  @Output()
  Stream get showDialogChange => onShowDialogChange.stream;
  ...
  void closeTheDialog() {
    showDialog = false;
    onShowDialogChange.add(showDialog);
  }

Of course, another option is to copy the EventEmitter class into your own project. Interesting to see AngularDart using core Dart classes, perhaps the start of a larger divergence of the two codebases.

Looking back to the first build of NP8080, the output JS was 300k(ish). The current build is around 200k JS which is great improvement considering the increase of application code over that time. When you consider a basic Dart web app is around 110k, it is even more impressive to have Angular framework squeezed into <90k.

Please raise an issue if you have a feature request. PRs welcome too!