Dependency Injection

The router functions as well as the controller classes and controller methods can define arbitrary dependencies, which are resolved by the dependency injection container. For example, it is possible to conveniently get to a database abstraction or logger.

For example, if a database has been provided as a provider, it can be injected:

class Database {
    //...
}

const app = new App({
    providers: [
        Database,
    ],
});

Functional API:

router.get('/user/:id', async (id: number, database: Database) => {
    return await database.query(User).filter({id}).findOne();
});

Controller API:

class UserController {
    constructor(private database: Database) {}

    @http.GET('/user/:id')
    async userDetail(id: number) {
        return await this.database.query(User).filter({id}).findOne();
    }
}

//alternatively directly in the method
class UserController {
    @http.GET('/user/:id')
    async userDetail(id: number, database: Database) {
        return await database.query(User).filter({id}).findOne();
    }
}

See Dependency Injection to learn more.

Scope

All HTTP controllers and functional routes are managed within the http dependency injection scope. HTTP controllers are instantiated accordingly for each HTTP request. This also means that both can access providers registered for the http scope. So additionally HttpRequest and HttpResponse from @deepkit/http are usable as dependencies. If deepkit framework is used, SessionHandler from @deepkit/framework is also available.

import { HttpResponse } from '@deepkit/http';

router.get('/user/:id', (id: number, request: HttpRequest) => {
});

router.get('/', (response: HttpResponse) => {
    response.end('Hello');
});

It can be useful to place providers in the http scope, for example to instantiate services for each HTTP request. Once the HTTP request has been processed, the http scoped DI container is deleted, thus cleaning up all its provider instances from the garbage collector (GC).

See Dependency Injection Scopes to learn how to place providers in the http scope.