In angular we can manually access and inject dependencies using the built in Injector class. By which you can access Injectables and Inject them without actually passing them in the constructor. Basically I want to inject a service to another service without passing it as an arg to the constructor.
This is the angular equivalent Inject a service manually
I wanted to achieve similar thing in nestjs
Note : The service to be injected also has a dependency, so I can't just instantiate it
I believe what you're looking for is Nest's ModuleRef class, where you can do something like the following:
#Injectable()
export class CatsService implements OnModuleInit {
private service: Service;
constructor(private moduleRef: ModuleRef) {}
onModuleInit() {
this.service = this.moduleRef.get(Service);
}
}
Where Service should actually be the class you are wanting to inject.
I think #Inject('token') should work as you expected
import { Injectable, Inject } from '#nestjs/common';
#Injectable()
export class HttpService<T> {
#Inject('HTTP_OPTIONS')
private readonly httpClient: T;
}
ref: https://docs.nestjs.com/providers#property-based-injection
Related
I am using Nest JS v8 and Type ORM v8.1.2. I want to create custom repository such as following sample and add custom methods to it. but the version of Type ORM doesn't support this feature.
#EntityRepository(User)
export class UserRepository extends Repository<User>
customFind() {}
}
Tip: Actually i want make a generic repository.
How can i implementing it?
Thanks for helping :)
Typeorm current version doesn't support this feature, you can try this method to create your custom repository
#Injectable()
export class UserRepository {
constructor(
#InjectRepository(UserEntity)
private readonly repository: BaseRepository<UserEntity>,
) {}
get instance() {
return this.repository;
}
}
at ^0.2.45 version
#EntityRepository(UserEntity)
export class UserRepository extends BaseRepository<UserEntity> {}
note: i'm using BaseRepository in typeorm-transactional-cls-hooked
Yes that can be done. With custom repositories, the DI is not managed by Nestjs. I learned that the hard way. The trick is to use getCustomRepository.
This is how you would do it
#EntityRepository(SomeEntity)
export class SomeCustomRepository extends Repository<SomeEntity> {
customFind() {}
}
#Injectable()
export class SomeService {
async doStuff() {
const repository = getCustomRepository(
SomeCustomRepository
);
repository.doStuff()
}
}
I have service which use service form global module and parametr.
#Injectable()
export class UsersService {
_paramentr;
constructor(
parametr,
GlobalService,
) {
this._parametr = parametr;
}
}
How to inject UsersService to AnotherService with paramentr.
I know, I can do it by new UsersService, but inside UserService I can use anothore services, I must inject it from top level to deep into. It's not very convenient.
I am working with Nest.js + TypeORM and hit a snag when trying to add inheritance to service classes.
I want to have a User service class that extends off of a Base service class, inheriting all the methods the it has.
This is what I've done:
export class BaseService<T> {
private repo;
constructor(repo: Repository<T>){
this.repo = repo;
}
async findAll(opts?): Promise<T[]> {
return this.repo.find(opts);
}
......
}
Then on my User service:
export class UserService extends BaseService<User> {
constructor(
#InjectRepository(User)
private userRepository: Repository<User>,
private readonly mailerService: MailerService,
) {
super(userRepository);
}
}
This works fine where I just need a single repository in the Service class but once I need more such as productRepository, as you can see it would fail due to constructor being hardcoded to accept a single repository.
I can't seem to figure out what would be the most elegant way of achieving something like this.
Does anyone know?
It is an old thread, anyways I meat this same problem and this answer may help someone else...
You can have an abstract class with common functions and boilerplate that you wich to be available in all your repositories to maintain patterns and so on...
export abstract class BaseService<T extends ObjectLiteral> {
protected repo: Repository<T>;
async findAll(opts?): Promise<T[]> {
return this.repo.find(opts);
}
......
}
Observe that constructor is omitted here and as an abstract class you should never have an instance of it, it is meant to be just an extension with common boilerplates and features that you don't want to write every single time you need a new service with the same features like a CRUD service or so...
Then you will use it like this:
export class UserService extends BaseService<User> {
constructor(
#InjectRepository(User) protected readonly repo: Repository<User>,
private readonly mailerService: MailerService,
) {
super();
}
...... extended stuff
}
I'm not sure if you need to inject repo with the same name and visibility but as it worked for me I didn't dive any further to get to know...
The bad side of this approach to me is that even if you don't have anything else to inject via constructor in your service you need to declare constructor and inject the base repository... it is a boilerplate that could be avoided too but I couldn't achieve this right now...
I have a guard that checks the ownership of a resource. If the user is the owner (created that resource), then he can access (update, read, delete).
Each resource is handled by its own service (comments is handled by the CommentsModule which has the CommentsService and so on). Each service that handles a resource with ownership implements a function called hasOwnership and the guard will call said function.
If possible, I would like my guard to inject the correct service depending on the controller that is calling it. So, if CommentsController is calling the guard, then it should inject and use CommentsService.hasOwnership.
I have tried using dynamic modules to inject the correct module/service on the imports of ACModule which hosts the guard, but that seems to be a no go as I can't properly handle the circular dependencies.
Injecting every service into the guard and selecting the correct will be very troublesome to mantain, due to the circular dependencies.
Is there a better way? This would be the desirable behavior.
#Injectable()
export default class ACGuard implements CanActivate {
constructor(
#Inject('SERVICE_KEY') private correctService
) {}
canActivate(context: ExecutionContext) {
return await correctService.hasOwnership();
}
}
Because you need a different service at run time (instead of at compile time) you are going to need to take a factory approach. It is a little troublesome to maintain as new resources are added but that's the trade-off you have to make.
First thing I would do is create a factory class to determine which service is the correct service to use based on the ExecutionContext:
export interface IService {
hasOwnership() : Promise<boolean>;
}
#Injectable()
export class ServiceFactory {
//Make sure every service returned from this method implements the "IService" interface
public getCorrectService(context: ExecutionContext) : IService {
if(context...) {
return new CommentsService();
} else if(context...) {
return new SomeOtherService();
}
}
}
Now you can inject that factory into your guard to get the correct service:
#Injectable()
export default class ACGuard implements CanActivate {
constructor(private serviceFactory: ServiceFactory) {}
canActivate(context: ExecutionContext) {
//Here's where the magic of this happens...
const correctService: Iservice = this.serviceFactory.getCorrectService(context);
return await correctService.hasOwnership();
}
}
I want to create an instance of a dynamically loaded class trough Nest.js dependency injection service.
In Angular I would use Injector.create, what would be the equivalent in Nest.js ?
First of all you should get a ModuleRef which references current module, and then use its "get" method to get an instance.
#Injectable()
export class AppletService {
files: FileService;
constructor(
private moduleRef: ModuleRef,
) {
this.files = moduleRef.get(FileService);
}
}