Multiple Services

In some scenarios, you may want to store multiple instances of a service in your container. Using get wouldn't accomplish this, as subsequent calls would provide the same instance.

However, one important feature of TypeDI is its ability to allow you to store multiple values under one ID. Let's explore this below with a quick example.

Let's consider the example of an application which needs to store information about multiple users. Some users have different roles, which we'll also need to represent via individual services.

src/user.class.ts

export class UserService {
  public readonly role = 'user';
  constructor(public name: string) {}
}

Now, let's create a ManagerService to represent managers. Managers should have the ability to perform administrative actions, so we'll add a deleteComment method.

src/manager-user.class.ts

import { User } from './user.class';

export class Manager extends User {
  public readonly role = 'manager';

  constructor(public name: string) {
    super(name);
  }

  deleteComment(commentId: string) {
    // ...
  }
}

To store each user, we'd also want a Token that we can use to reference them. Let's do this below.

src/app.ts

import { Container } from '@freshgum/typedi';
import { User } from './user.class';

export const USER = new Token<User>();

const joe = new User('Joe');
const rick = new ManagerUser('Rick');

function addUser(value: User) {
  Container.set({ id: USER, multiple: true, value, dependencies: [] });
}

addUser(joe);
addUser(rick);

note

The advantage of this approach is that it's much easier to keep track of each service instance, as they're all stored in one container.

You'll notice that while we can store individual users, we can't currently access them. Let's fix that.

src/app.ts

// ...

function getUsers() {
  return Container.getMany(USER);
}

console.log(getUsers());
// -> [class User, class ManagerUser]

There we go! There's a basic example of how to use multiple services in TypeDI.