Observer Pattern in Fastify

Overview

Define a one-to-many dependency between objects

Observer Pattern 1 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

Pino Logger

Structured logging with Pino

npx hanma add fastify-logger --framework fastify

Multiple log levelsSensitive field redactionPretty print in development

Basic Example

// Observer Pattern implementation example
// This shows the basic structure of observer pattern in Fastify

// 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 ObserverRepository 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 ObserverRepository();
const items = await repository.findAll();

Frequently Asked Questions

What is Observer Pattern?

Define a one-to-many dependency between objects. It's a well-established software design pattern that helps organize code for better maintainability and testability.

How does Observer Pattern work with Fastify?

Fastify 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.