nano-ioc

simple-ioc

Very simple container class to handle inversion of control

##Features

1. Any type of value can be added (object, function, primitive)
2. Lazy initialisation, so order in which values/services are added isn't important
3. Circular dependencies partially handled - it's surprising that TypeScript doesn't detect unresolvable chicken/egg dependencies like this

class Chicken {
  private egg: Egg;

  constructor(e: Egg) {
    this.egg = e;
  }
}

class Egg {
  private chicken: Chicken;

  constructor(c: Chicken) {
    this.chicken = c;
  }
}

##Limitations

1. Circular dependencies are detected when values are accessed and thrown as CircularDependencyError
2. To access the dynamically defined container properties, the container instance must be asserted as type any, which is annoying but unavoidable

const c = new Container() as any;
c.register('person', () => new Person({ name: 'Frank Zappa' }));
c.register('driver',  () => new Driver(c.person));

###Usage Hopefully self-explanatory from this example. Note that the order in which dependent services are added to the container is not important

const c = new Container() as any;

c.register('driver',  () => new Driver(c.person));
c.register('person', () => new Person({ name: 'Jimi Hendrix' }));

const retrievedDriver = c.driver;

##Notes

• I would have liked to have developed a functional programming paradigm solution, but I couldn't see a way to abstract this approach into a meaningful library
• I wouldn't normally aim for 100% coverage in unit testing unless this was a formal requirement. For (potentially) widely used libraries, this seems a reasonable goal
• Published on NPM as nano-ioc@1.0.0 - in the unlikely event that someone else starts using it, they might spot bugs or improvements ☺️