Assisted injection in Aurelia?

Question

I have a class whose constructor has two arguments; one is a dependency, the other is a configuration property:

@inject(Dependency)
class MyClass{
  constructor(dependency, config){
  }
}

How can I make use of Aurelia's dependency injection to automatically inject the dependency but allow the class's consumer to specify the config value?

Answer 1

Here are some options:

---

Option 0: Factory Resolver

foo.js

import {inject} from 'aurelia-framework';
import {FooDependency} from './foo-dependency';

@inject(FooDependency)
export class Foo {
  constructor(dep, config) {
  }
}

needs-foo.js

import {inject, Factory} from 'aurelia-framework';
import {Foo} from './foo';

@inject(Factory.of(Foo))
export class NeedsFoo {
  constructor(fooFactory) {
    let config = {};
    this.foo = fooFactory(config);
  }
}

---

Option 1: Factory

foo.js

import {inject} from 'aurelia-framework';
import {FooDependency} from './foo-dependency';

class Foo {
  constructor(dep, config) {
  }
}

@inject(FooDependency)
export class FooFactory {
  constructor(dep) {
    this.dep = dep;
  }

  makeFoo(config) {
    return new Foo(this.dep, config);
  }
}

needs-foo.js

import {inject} from 'aurelia-framework';
import {FooFactory} from './foo';

@inject(FooFactory)
export class NeedsFoo {
  constructor(fooFactory) {
    let config = {};
    this.foo = fooFactory.makeFoo(config);
  }
}

---

Option 2: Child Container

foo.js

import {inject} from 'aurelia-framework';
import {FooDependency} from './foo-dependency';

export const configKey = 'config';

@inject(FooDependency, configKey)
export class Foo {
  constructor(dep, config) {
  }
}

needs-foo.js

import {inject, Container} from 'aurelia-framework';
import {Foo, configKey} from './foo';

@inject(Container)
export class NeedsFoo {
  constructor(container) {
    let config = {};
    let childContainer = container.createChild();
    childContainer.registerInstance(configKey, config);
    this.foo = childContainer.get(Foo);
  }
}

---

Option 3: Brute Force

foo.js

export class Foo {
  constructor(dep, config) {
  }
}

needs-foo.js

import {inject, Container} from 'aurelia-framework';
import {FooDependency} from './foo-dependency';
import {Foo} from './foo';

@inject(Container)
export class NeedsFoo {
  constructor(container) {
    let config = {};
    let dep = container.get(FooDependency);
    this.foo = new Foo(dep, config);
  }
}