Connect MongoDB

Goal for this step

Set up MongoDB dependencies, create environment files, and configure Nest so the app can talk to the database.

1. Install MongoDB + validation libraries

• npm install these packages so Nest can talk to MongoDB, validate inputs, and read .env files:

npm install @nestjs/mongoose mongoose nestjs-zod zod @nestjs/config

• @nestjs/mongoose is the Nest bridge for MongoDB.
• mongoose is the official MongoDB driver.
• nestjs-zod integrates Zod with Nest so we can define DTOs using schemas.
• @nestjs/config loads .env files automatically so process.env has the values you just captured.

2. Confirm your .env files

You should already have .env.example and .env.development.local from the Prepare MongoDB step. Double-check they contain the right connection string for the option you chose:

• Docker users keep USE_ATLAS=false and rely on the default MONGODB_URI.
• Atlas users set USE_ATLAS=true and paste the long connection string into MONGODB_URI_ATLAS.

If you skipped the previous page, go back and complete those steps before continuing.

3. Configure AppModule

Edit src/app.module.ts so Nest loads environment files before reading them and falls back sensibly.

import { Module } from '@nestjs/common';
import { ConfigModule, ConfigService } from '@nestjs/config'; 
import { MongooseModule } from '@nestjs/mongoose'; 

@Module({
  imports: [
    // Module to load environment variables
    ConfigModule.forRoot({ 
      isGlobal: true, 
      envFilePath: ['.env.development.local', '.env'], 
    }), 
    // Module to connect to MongoDB
    MongooseModule.forRootAsync({ 
      inject: [ConfigService], 
      useFactory: (config: ConfigService) => { 
        const useAtlas = config.get<string>('USE_ATLAS') === 'true'; 
        const uri = useAtlas 
          ? config.get<string>('MONGODB_URI_ATLAS') 
          : config.get<string>('MONGODB_URI'); 
        if (!uri) { 
          throw new Error('Missing MongoDB URI. Check your .env values.'); 
        } 
        return { uri }; 
      }, 
    }), 
  ],
  controllers: [],
  providers: [],
})
export class AppModule {}

For now the module only connects to MongoDB. Later pages will add new modules and controllers.

With MongoDB running and AppModule wired up (including the config loader), you are ready to create schemas. Continue to Model to define the Task collection.

Commit your AppModule changes

Before pushing, capture the configuration updates you just made:

git add src/app.module.ts
git commit -m "feat: configure mongodb connection"

Push your branch and open a pull request

Stay on your feature/environment-config branch and push it to GitHub:

git push -u origin feature/environment-config

Then open a pull request targeting main. Add a short summary (what changed, any screenshots of .env samples) and request a teammate review. When reviewers approve, choose Squash and merge so the entire branch becomes a single commit on main (for example, feat: configure environment & mongodb).

Once merged, pull the latest main locally before starting the next chapter.