DI-Injectable

A simple Dependency Injection (DI) library for TypeScript supporting Singleton and Transient service lifetimes.

Installation

First, install the package via npm or yarn:

npm install di-injectable

yarn add di-injectable

Usage

Setting Up Services

• Define Services: Create your service classes and use the @Injectable decorator and use ServiceLifetime enum to register your services as Singleton or Transient..
• Resolve Services: Use the ServiceProvider to resolve instances of your services.

Example

Let's walk through a complete example.

1. Define Services Create some simple services and use the @Injectable decorator.

// src/services/logger.ts
import { Injectable } from 'di-injectable'; 

@Injectable(ServiceLifetime.Singleton)
export class Logger {
  log(message: string) {
    console.log(`Logger: ${message}`);
  }
}

// src/services/userService.ts
import { Injectable, Inject } from 'di-injectable';
import { Logger } from './logger';

@Injectable()
export class UserService {
  constructor(@Inject(Logger) private logger: Logger) {}

  getUser() {
    this.logger.log('Getting user...');
    return { id: 1, name: 'John Doe' };
  }
}

2. Resolve Services Use the ServiceProvider to resolve instances of your services.

// src/app.ts
import { ServiceProvider } from 'di-injectable';
import { UserService } from './services/userService';

const serviceProvider = new ServiceProvider();

const userService = serviceProvider.resolve<UserService>(UserService);
const user = userService.getUser();
console.log(user);

Explanation

• Defining Services:
  • The Logger service is a simple logger class.
  • The UserService class depends on the Logger service. The @Inject decorator is used to inject the Logger service
  • into the UserService constructor.
• Registering Services:
  • We register the Logger service as a Singleton, meaning only one instance of Logger will be created and shared.
  • We register the UserService as a Transient by default, meaning a new instance of UserService will be created every time it is resolved.
• Resolving Services:
  • We create a ServiceProvider instance.
  • We resolve an instance of UserService using the serviceProvider. The UserService will have the Logger instance injected into it due to the @Inject decorator.

Service Lifetimes

• Singleton: Only one instance of the service is created and shared.
• Transient: A new instance of the service is created every time it is requested.

API Reference

• ServiceProvider:
  • resolve<T>(token: any): T: Resolves an instance of the service.
  • Injectable: Decorator to mark a class as injectable as register it.
  • Inject: Decorator to inject dependencies into the constructor.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT

Steps to Use

1. Create Your Services: Define your services using the @Injectable decorator and use ServiceLifetime enum to register your services as Singleton or Transient.
2. Resolve Services: Use ServiceProvider to resolve instances of your services.