Dependency Injection Guide

Overview

NitroStack uses a dependency injection (DI) container for managing class dependencies, making your code testable and modular.

@Injectable Decorator

Mark classes for injection:

import { Injectable } from 'nitrostack';

@Injectable()
export class UserService {
  async findById(id: string) {
    return { id, name: 'John Doe' };
  }
}

Constructor Injection

Inject dependencies via constructor:

export class UserTools {
  constructor(
    private userService: UserService,
    private emailService: EmailService,
    private db: DatabaseService
  ) {}
  
  @Tool({ name: 'create_user' })
  async createUser(input: any) {
    const user = await this.userService.create(input);
    await this.emailService.sendWelcome(user.email);
    return user;
  }
}

Service Lifecycle

Services are singletons by default - one instance for the entire application.

Circular Dependencies

Avoid circular dependencies in constructors. If needed, use @Inject() with forward references.

Best Practices

Inject services, not classes - Keep logic in services
Use interfaces - Program to abstractions
Avoid new keyword - Let DI container create instances
Test with mocks - Easier with DI