In Inversify.js there is multiInject decorator that allow us to inject multiple objects as array. All objects' dependencies in this array resolved as well.

Is there any way to achieve this in Nest.js?

In Inversify.js there is multiInject decorator that allow us to inject multiple objects as array. All objects' dependencies in this array resolved as well.

Is there any way to achieve this in Nest.js?

• javascript
• node.js
• nestjs
• inversifyjs

2 Answers 2

There is no direct equivalent to multiInject. You can provide an array with a custom provider though:

Example

Try the example live in this sandbox.

Injectables

Let's assume you have multiple @Injectable classes that implement the interface Animal.

export interface Animal {
  makeSound(): string;
}

@Injectable()
export class Cat implements Animal {
  makeSound(): string {
    return 'Meow!';
  }
}

@Injectable()
export class Dog implements Animal {
  makeSound(): string {
    return 'Woof!';
  }
}

Module

The classes Cat and Dog are both available in your module (provided there or imported from another module). Now you create a custom token for the array of Animal:

providers: [
    Cat,
    Dog,
    {
      provide: 'MyAnimals',
      useFactory: (cat, dog) => [cat, dog],
      inject: [Cat, Dog],
    },
  ],

Controller

You can then inject and use the Animal array in a Controller like this:

constructor(@Inject('MyAnimals') private animals: Animal[]) {
  }

@Get()
async get() {
  return this.animals.map(a => a.makeSound()).join(' and ');
}

This also works if Dog has additional dependencies like Toy, as long as Toy is available in the module (imported/provided):

@Injectable()
export class Dog implements Animal {
  constructor(private toy: Toy) {
  }
  makeSound(): string {
    this.toy.play();
    return 'Woof!';
  }
}

Just a minor tweak to the great solution by @kim-kern you can use that solution but avoid a small bit of overhead for adding new entries ...

replace

providers: [
    Cat,
    Dog,
    {
      provide: 'MyAnimals',
      useFactory: (cat, dog) => [cat, dog],
      inject: [Cat, Dog],
    },
  ],

with

providers: [
    Cat,
    Dog,
    {
      provide: 'MyAnimals',
      useFactory: (...animals: Animal[]) => animals,
      inject: [Cat, Dog],
    },
  ],

It's only minor but instead of having to add a new one in 3 places for every new addition it's down to 2. Adds up when you have a few and reduces chance of error.

Also the nest team are working on making this easier an you can track via this github issue: https://github.com/nestjs/nest/issues/770