Example on how to get providers into dynamic objects

wizard.ts

import { INestApplication, Injectable, Logger, Module } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';

/**
 * A kind of hero that casts spells.
 */
class Wizard {
	constructor(
		private readonly name: string,
		private readonly level: number,
		private readonly environmentService: EnvironmentService
	) { }

	public castFire(): void {
		if (this.environmentService.isRainy()) {
			throw new Error('Cannot cast fire if it rains');
		}

		// cast fire
		// ...
	}
}

/**
 * To query information about the environment a hero is currently in.
 */
@Injectable()
class EnvironmentService {
	public isRainy(): boolean {
		return true;
	}
}

/**
 * Factory to create heroes of various kinds. Allows injecting other services into
 * heroes.
 */
@Injectable()
class HeroFactory {
	constructor(private readonly environmentService: EnvironmentService) { }

	public createWizard(name: string): Wizard {
		return new Wizard(name, 1, this.environmentService);
	}
}

@Module({
	providers: [
		HeroFactory,
		EnvironmentService
	]
})
export class GameModule { }

/**
 * Run the example
 */
const runGame = async (): Promise<void> => {
	const app: INestApplication = await NestFactory.create(GameModule);
	const heroFactory = app.get<HeroFactory>(HeroFactory);
	const wizard = heroFactory.createWizard('Robin');
	wizard.castFire();
};

runGame().catch((error: Error): void => {
	Logger.error(error);
});

/*
Output:

ts-node-esm wizard.ts
[Nest] 19273  - 03/13/2023, 11:51:32 AM     LOG [NestFactory] Starting Nest application...
[Nest] 19273  - 03/13/2023, 11:51:32 AM     LOG [InstanceLoader] GameModule dependencies initialized +19ms
[Nest] 19273  - 03/13/2023, 11:51:32 AM   ERROR Error: Cannot cast fire if it rains
 */