Hooks

Hooks in NodeArch allow you to execute code when the application starts and when it shuts down.
They are ideal for managing resources like database connections, job schedulers, cache warmups, and other startup/shutdown tasks.

This guide will walk you through how to properly create, decorate, and implement a Hook in NodeArch.

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What Is a Hook?

A Hook in NodeArch is a class that:

• Implements the IHook interface
• Is decorated with the @Hook() class decorator

This allows NodeArch to automatically discover, instantiate, and execute your hook at the right time.

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Hook Interface

Here’s the official IHook interface:

export interface IHook {
  onStart?(): Promise<void>;
  onStop?(): Promise<void>;
}

You can implement either onStart, onStop, or both — they are optional.

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Hook Decorator

The @Hook() decorator marks your class as a lifecycle hook component.

It can accept optional options based on the IComponentOptions interface:

export interface IComponentOptions {
  scope?: ComponentScope;
  namespace?: string;
  export?: boolean;
}

export enum ComponentScope {
  REQUEST = 'Request',
  SINGLETON = 'Singleton',
  TRANSIENT = 'Transient'
}

Common options you can set:

Option	Description	Default
export	Whether to export this component to other apps	false

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Example: Creating a Hook

Let’s create a simple hook that logs when the application starts and stops.

import { Hook } from '@nodearch/core';
import { IHook } from '@nodearch/core';

@Hook()
export class LoggerHook implements IHook {

  async onStart(): Promise<void> {
    console.log('🚀 Application has started.');
  }

  async onStop(): Promise<void> {
    console.log('🛑 Application is stopping.');
  }
}

✅ Because the class is decorated with @Hook() and implements IHook, NodeArch automatically detects it and calls onStart and onStop at the appropriate times.

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Best Practices

• Keep your hooks focused — each hook should manage a single responsibility (e.g., database, scheduler, cache).
• Avoid blocking operations in onStart and onStop — use await properly for async tasks.

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Summary

• Hooks manage logic during the app's lifecycle (start/stop).
• Hooks must:
  • Implement IHook
  • Be decorated with @Hook()
• NodeArch handles discovery and execution automatically.
• Use lifecycle hooks to manage database connections, start background workers, register external services, and more.

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NodeArch Hooks are a clean, powerful way to control your app’s lifecycle — without manual boilerplate.