An IoC Container for Dart (with Autofac like API)

I enjoy throwing Darts, and have been using it quiet a bit recently. The OO nature of Dart makes it suitable for most OO design patterns. I use the inversion of control patter almost everywhere, but Dart did not have a good IoC container library that I knew of. Hence, in order to give something back to the community I wrote a lightweight IoC container based on the API of my favorite “Autofac”. The main reason for this choice was that a C# programmer who has already worked with Autofac can start using “Autodart” in a few minutes!

Below is a sample of how Autodart can be used:

class Baz{
}

class Bar{
  Baz baz;
  Bar(this.baz);
}

class Foo{
  Bar bar;
  Foo(this.bar);
}
void main(){
  var b = new AutoBuilder();
  b.register((c, p) => new Baz())
    .As("Baz")
    .singleInstance();

  b.register((c, p) => new Bar(c.resolve("Baz")))
    .As("Bar")
    .instancePerLifetimeScope();

  b.register((c, p) => new Foo(c.resolve("Bar")))
    .As("Foo"); //Default is .instancePerDependency()

  var c = b.build();

  var foo = c.resolve("Foo") as Foo;
  var foo2 = c.resolve("Foo") as Foo;

  assert(foo != foo2);
  assert(foo.bar === foo2.bar);
  assert(foo.bar.baz === foo2.bar.baz);

  /*
    Other supported API include:
    b.register(..).As(..).externallyOwned();
    c.resolveLazy("Foo") as Lazy<Foo>;
    var childScope = c.createLifetimeScope();
    c.dispose(); //Disposes all disposables in the scope
  */
}

Autodart supports the following scopes: SingeInstance (Singleton), InstancePerLifetimeScope (Nester Scopes), and InstancePerDependency.

It also defines the Disposable concept, and manages the scopes for Disposable objects.

Shortcomings: There is no auto wiring, as Dart does not yet support reflection. Also there is still no “Type” type in Dart, so string type names are used as keys. I would update the library as soon as dart adds support for reflection.

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Dart, an effort from google to liberate the Web

I enjoy writing javascript code, but to be honest, the fact that javascript has no types, and anything imaginable is a valid code in javascript – therefore not much productivity tooling is possible – makes me not a fan of it for serious development.

I may dislike JS for serious development sometimes, but there are times that I truly hate JS!

When I say I sometimes hate JS, I am not joking, and it is not related to the features and looks of the language either. The sole reason for my feeling is that JS is the “Dictator” of the web. It imposes itself on you! It doesn’t care if you believe it is the right tool for your job or not, you “have to” love it! It kicked flash out, killed other competitors and now, it is the sole ruler of the web. The great dictator of the web if you like. And I hate dictators, even if they are not evil.

As is the case in any other dictatorships, there are liberating movements here and there. Google have been a pioneer of such movement from the GWT times. Microsoft tried to challenge JS power with Silverlight, a move that was repressed quickly. Google acted smarter, it did not try to challenge the power of JS, it worked with it and tried to make JS to bend to democratic “reforms”. By chromium’s V8 and other efforts to improve performance of JS, it became possible to compile to JS.

I don’t think compiling JS would completely solve the problem (I would much rather we had some VM specifications for browser instead of a language), but it is the best hope for now. The proof is that in 2012, close to two decades from the first version of JS, we still don’t have a complex JS based product that works fine. Even the most expensive and sought after products fail supporting different browsers gracefully. Yahoo mail has a big team of best JS devs in the world working on it, and yet after years, it still sucks in Chrome.

Dart however, is a lovely language. It stands somewhere between strongly typed languages like Java and C#, and java script. It takes best of the two worlds and has a modern, but familiar syntax, which is quick to learn and coding in Dart needs close to zero boilerplating.

  main() {
    print("Hello world! From Dart!");
  }

What makes Dart different, is that it compiles to JS. It is designed to compile to JS from scratch. Hence, you could imagine it would do the job better than others.

Other things that make Dart different are that first, it is supported by google, and second it has a couple of nice IDEs from start. Google support makes me believe Dart has a future (a bright one maybe) and good tooling makes it useful from the earliest version.

In the next posts, I will talk about some libraries I have developed for Dart. And in the future I would use Dart more often.