Optional Dependencies

You can declare an optional dependency using the standard TypeScript syntax:

ApiService.ts

import { injected } from 'brandi';
import { TOKENS } from './tokens';
import { Logger } from './Logger';

export class ApiService {
  /*                        ↓ The optional dependency. */
  constructor(private logger?: Logger) {}
}

And inject it using the optional token field:

ApiService.ts

injected(
  ApiService,
  TOKENS.logger.optional /* ← The optional dependency token. */,
);

When using optional tokens, the Brani container will not throw an error if the dependency is not bound in the container, but will return undefined.