Dependency Injection

luna provides a simple dependency injection pattern to define your services and inject them into your components at runtime.

Define a service

To define a service, you have to decorate it with the LunaService decorator and provide a name.

// auth-service.js

import { LunaService } from '@webtides/luna-js';

@LunaService({
    name: 'auth-service'
})
export default class AuthService {
    async loadUserById(id) {
        return MagicDB.queryById(id);
    }
}

Use a service

To use a service, you can inject it using the Inject decorator which luna provides.

// example-component.js
import { Inject } from '@webtides/luna-js';
import AuthService from '../services/auth-service.js';

export default class ExampleComponent {
    @Inject(AuthService) authService;
    
    async loadDynamicProperties({ request }) {
        return {
            user: await this.authService.loadUserById(request.userId),
        };
    }
}

Gotchas: The dependency injection currently only works on the server context. All injected services will be stripped out on the client. This has the advantage that sensitive information and logic will stay on the server.

In the way this example is build the AuthService class will never be included inside the client bundle if you are building for production. If you are not building for production, the source-maps will still contain the original code for a better debugging experience.

The current request

Sometimes you need the current request inside a service or component. For that luna provides a CurrentRequest decorator. This request will be the default express request object.

// auth-service.js
import { LunaService, CurrentRequest } from '@webtides/luna-js';

@LunaService({
    name: 'auth-service'
})
export default class AuthService {
    @CurrentRequest request;
    
    async loadUserById(id) {
        return MagicDB.queryById(id);
    }
    
    async loadCurrentUser() {
        return this.loadUserById(this.request.userId);
    }
}

Gotchas: The CurrentRequest decorator can only be used inside components or services that are injected into components.