Repository Pattern in NestJS

Overview

Decouple data access layer from business logic

Repository Pattern 2 implementations available

When to Use

When you need to abstract data access logic
When you want to make your code testable
When you need to support multiple data sources
When you want to decouple business logic from infrastructure

Available Implementations

Prisma Exception Filter

Prisma database error handling

npx hanma add prisma-exception-filter --framework nest

Unique constraint errorsNot found errorsForeign key errors

Health Indicators

Health check services

npx hanma add health-provider --framework nest

Database healthRedis healthMemory usage

Basic Example

// Repository Pattern implementation example
// This shows the basic structure of repository pattern in NestJS

// Define your interface
interface IRepository {
  findAll(): Promise<T[]>;
  findById(id: string): Promise<T | null>;
  create(data: CreateDto): Promise<T>;
  update(id: string, data: UpdateDto): Promise<T>;
  delete(id: string): Promise<void>;
}

// Implement the pattern
class RepositoryRepository implements IRepository {
  async findAll(): Promise<T[]> {
    // Implementation
  }

  async findById(id: string): Promise<T | null> {
    // Implementation
  }

  async create(data: CreateDto): Promise<T> {
    // Implementation
  }

  async update(id: string, data: UpdateDto): Promise<T> {
    // Implementation
  }

  async delete(id: string): Promise<void> {
    // Implementation
  }
}

// Use the pattern
const repository = new RepositoryRepository();
const items = await repository.findAll();

Frequently Asked Questions

What is Repository Pattern?

Decouple data access layer from business logic. It's a well-established software design pattern that helps organize code for better maintainability and testability.

How does Repository Pattern work with NestJS?

NestJS provides excellent support for this pattern through its dependency injection system and middleware composition.

What are the benefits?

Improved testability, separation of concerns, easier maintenance, and flexibility to change implementations without affecting business logic.

When should I avoid this pattern?

For very simple applications with minimal logic, the pattern may add unnecessary complexity. Use judgment based on project requirements.