IOC for TypeScript

Question

With TypeScript now we have static analyze and many OOP features in JavaScript. So it's also time to have better unit tests in client side logic and as well we need IOC container for dependency injections to make code more testable...

So, have someone already experienced it this subject or maybe know libraries for typescript or JavaScript frameworks that can be porting to TypeScript?

Answer 1

I have developed an IoC container called InversifyJS with advanced dependency injection features like contextual bindings.

You need to follow 3 basic steps to use it:

1. Add annotations

The annotation API is based on Angular 2.0:

import { injectable, inject } from "inversify";

@injectable()
class Katana implements IKatana {
    public hit() {
        return "cut!";
    }
}

@injectable()
class Shuriken implements IShuriken {
    public throw() {
        return "hit!";
    }
}

@injectable()
class Ninja implements INinja {

    private _katana: IKatana;
    private _shuriken: IShuriken;

    public constructor(
        @inject("IKatana") katana: IKatana,
        @inject("IShuriken") shuriken: IShuriken
    ) {
        this._katana = katana;
        this._shuriken = shuriken;
    }

    public fight() { return this._katana.hit(); };
    public sneak() { return this._shuriken.throw(); };

}

2. Declare bindings

The binding API is based on Ninject:

import { Kernel } from "inversify";

import { Ninja } from "./entities/ninja";
import { Katana } from "./entities/katana";
import { Shuriken} from "./entities/shuriken";

var kernel = new Kernel();
kernel.bind<INinja>("INinja").to(Ninja);
kernel.bind<IKatana>("IKatana").to(Katana);
kernel.bind<IShuriken>("IShuriken").to(Shuriken);

export default kernel;

3. Resolve dependencies

The resolution API is based on Ninject:

import kernel = from "./inversify.config";

var ninja = kernel.get<INinja>("INinja");

expect(ninja.fight()).eql("cut!"); // true
expect(ninja.sneak()).eql("hit!"); // true

The latest release (2.0.0) supports many use cases:

• Kernel modules
• Kernel middleware
• Use classes, string literals or Symbols as dependency identifiers
• Injection of constant values
• Injection of class constructors
• Injection of factories
• Auto factory
• Injection of providers (async factory)
• Activation handlers (used to inject proxies)
• Multi injections
• Tagged bindings
• Custom tag decorators
• Named bindings
• Contextual bindings
• Friendly exceptions (e.g. Circular dependencies)

You can learn more about it at https://github.com/inversify/InversifyJS

Answer 2

Alternatively you can just use no framework and use class as container with object factories as properties. You can then inherit this class in tests and change factories. This approach is type safe and do not require any decorators, just registration of classes.

class B {
    echo() {
        alert('test');
    }   
}

class A {
    constructor(private b: B) {
        b.echo();
    }
}

class Container {
    A = () => new A(this.B());
    B = singleton(() => new B()); 
}

var c = new Container();
var a = c.A();

// singleton helper:

function memoize<T>(factory: () => T): () => T  {
    var memo: T = null;
    return function () {
        if(!memo) {
            memo = factory();
        }
        return memo;
    };
}

var singleton = memoize;