MikroOrm Basics.ts

// Firstly, import MikroOrmModule in App.module
@Module({
  imports: [MikroOrmModule.forRoot(), CatsModule],
})
// The Database configuration is store in mikro-orm.config.ts
const config: Options = {
  entities: [Cat],
  dbName: 'postgres',
  type: 'postgresql',
  port: 5432,
  host: 'localhost',
  debug: true,
  user: 'postgres',
  password: 'postgres',
} as Options;

// The config paths are defined in package.json
  "mikro-orm": {
    "useTsNode": true,
    "configPaths": [
      "./src/mikro-orm.config.ts",
      "./dist/mikro-orm.config.js"
    ]
  }
// To use repository pattern, we register entities via forFeature() in feature module
@Module({
  imports: [MikroOrmModule.forFeature({ entities: [Cat] })],
})
export class CatsModule {}

// We inject the repository into service
  constructor(
    @InjectRepository(Cat)
    private readonly catRepository: EntityRepository<Cat>,
  ) {}
 // Then, we can perform database operation
this.catRepository.findOne(findOneOptions);