**Course Title:** Mastering NestJS: Building Scalable Server-Side Applications **Section Title:** Deployment and CI/CD Pipelines **Topic:** Managing environment variables and configurations **Overview** In this topic, we will explore the importance of managing environment variables and configurations in a NestJS application. We will discuss how to handle different environments, configure variables, and use a configuration service to manage application settings. **Why Manage Environment Variables and Configurations?** Environment variables and configurations play a crucial role in a NestJS application. They allow you to: * Handle different environments (development, production, testing) * Configure application settings (database connections, API keys) * Use a configuration service to manage application settings **Handling Different Environments** In a NestJS application, you can handle different environments using the `process.env` object. You can create environment-specific variables by setting them in your operating system or using a `.env` file. **Using a .env File** You can create a `.env` file in the root of your project to store environment-specific variables. For example: ```bash # .env file NODE_ENV=development DB_HOST=localhost DB_PORT=5432 DB_USER=myuser DB_PASSWORD=mypassword ``` You can then access these variables in your NestJS application using the `process.env` object. **Configuring Variables** You can configure variables in your NestJS application using the `@Config` decorator. For example: ```typescript // app.module.ts import { Module } from '@nestjs/common'; import { AppController } from './app.controller'; import { AppService } from './app.service'; import { ConfigModule } from '@nestjs/config'; @Module({ imports: [ ConfigModule.forRoot({ envFilePath: '.env', isGlobal: true, }), ], controllers: [AppController], providers: [AppService], }) export class AppModule {} ``` **Using a Configuration Service** You can use a configuration service to manage application settings. For example: ```typescript // config.service.ts import { Injectable } from '@nestjs/common'; import { ConfigService } from '@nestjs/config'; @Injectable() export class ConfigService { constructor(private readonly configService: ConfigService) {} getDatabaseUrl(): string { return this.configService.get('DB_HOST'); } DatabasePort(): number { return this.configService.get('DB_PORT'); } } ``` **Best Practices** When managing environment variables and configurations in a NestJS application, follow these best practices: * Use a `.env` file to store environment-specific variables * Use the `@Config` decorator to configure variables * Use a configuration service to manage application settings * Keep sensitive information (API keys, database passwords) secure **Conclusion** Managing environment variables and configurations is an essential part of building a scalable server-side application with NestJS. By following the best practices outlined in this topic, you can ensure that your application is secure, maintainable, and easy to deploy. **Additional Resources** * [NestJS Configuration Documentation](https://docs.nestjs.com/techniques/configuration) * [NestJS Environment Variables Documentation](https://docs.nestjs.com/techniques/environment-variables) **Leave a comment or ask for help if you have any questions or need further clarification on this topic.**

# .env file
NODE_ENV=development
DB_HOST=localhost
DB_PORT=5432
DB_USER=myuser
DB_PASSWORD=mypassword

// app.module.ts
import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { ConfigModule } from '@nestjs/config';

@Module({
  imports: [
    ConfigModule.forRoot({
      envFilePath: '.env',
      isGlobal: true,
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

// config.service.ts
import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

@Injectable()
export class ConfigService {
  constructor(private readonly configService: ConfigService) {}

  getDatabaseUrl(): string {
    return this.configService.get('DB_HOST');
  }

  DatabasePort(): number {
    return this.configService.get('DB_PORT');
  }
}