Dynamic Module async | NestJS | Page 1

craggy bridge Jul 7, 2023, 8:33 PM

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Hey guys!
I'm new to NestJS world, so i'm struggling a bit with something that might be trivial for you all.
I have the following scenario:

I have a lib(built in typescript), this lib is "mainly" a class, let's call it XPTOService. XPTOService main purpose is to make some SOAP calls, using soap library, which needs to instantiate a new Client in an async way.
This XPTOService has a method called build which will create a new instance of the Client class from soap pkg
This service has some other methods that will use that instance to make some SOAP calls

On the other side, i have my NestJS server, which will consume that library. I created a service, that will use that library, and access its available methods.
My problem here is, i need to initialize the lib first(calling the build method) before i can call any other method that relies on the Client instance, I've done some researches regarding Dynamic Module, but none of those articles that i read have a specific case like mine.

Anyone here knows how can i instantiate that lib inside my Service,calling the build method, and enable the whole application to use it?

low island Jul 7, 2023, 8:55 PM

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Sounds like all you need is a custom "factory provider" that will instantiate your soap client, which you can then inject to your service that will be exported from your custom library module.

junior cove Jul 7, 2023, 9:25 PM

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TIL that the factory is also singleton scoped, I thought it was scoped to transient. Always used module hooks to do these kind of things

craggy bridge Jul 7, 2023, 9:29 PM

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Could you guys explain that better? Again, i'm new here, and i thought this was something simple to accomplish

junior cove Jul 7, 2023, 9:32 PM

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They are saying that you can register it as a singleton provider e.g. (psuedo)

@Module({
  providers: [{
    useFactory: async () => {
      const soap = new Soap()
      await soap.build()

      return soap
    },
    provide: SomeToken
  }]
})
class AppModule {}

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and then you simply inject it in your constructor as usual

low island Jul 7, 2023, 9:32 PM

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junior cove TIL that the factory is also singleton scoped, I thought it was scoped to transi...

The factory can have the same scopes as a class - you can use the scope parameter.

junior cove Jul 7, 2023, 9:33 PM

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low island The factory can have the same scopes as a class - you can use the `scope` parame...

Yeah just found out! I thought it also had some magic behind it just like when you use request scoped providers where it changes the scope of another provider to be request scoped too

low island Jul 7, 2023, 9:34 PM

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junior cove Yeah just found out! I thought it also had some magic behind it just like when y...

Yeah, it does that, too. If you inject a request to the factory, then it becomes request scoped and called on each request

junior cove Jul 7, 2023, 9:35 PM

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Figured. Good to know!

craggy bridge Jul 7, 2023, 9:36 PM

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I think i got it, but i have the following scenario:

Controller > Service > Lib that needs to run build before its usage

I'm injecting the that lib inside the service, so i need that service to be loaded by NestJS and calls build from the lib, in that order

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So my controller can call its methods

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Let me know if i wasn't clear enough

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I have something like this:

// My module
@Module({
  imports: [],
  providers: [
    {
      provide: XPTO_TOKEN,
      useFactory: async () => {
        const xptoService = new XptoService()
        await xptoService.build()
        return xptoService
      },
    },
  ],
  exports: [XptoService],
})
export class XPTOModule {}

// My service
@Injectable()
export class XPTOService {
  private xptoSoapInstance: XPTOClient // This guy is being imported at the top of the file
  constructor() {}

  public async build() {
    this.xptoSoapInstance = new XPTOClient()
    await this.xptoSoapInstance.build() // <- this guy here is the lib that creates a new instance of the SOAP client
  }

  // rest of the service

// My service
@Controller('agency')
export class AgencyController {
  constructor(
    private agencyService: AgencyService,
    @Inject(XPTO_TOKEN) private xptoService: XPTOService,
  ) {}

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I put that Service if the middle, instead of simply calling the lib, because I have to parse the data that comes from the Lib, but i'm not sure if this is the right approach

junior cove Jul 7, 2023, 9:49 PM

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so the service has some logic and then builds the soap instance, after that, anyone can use the XPTOClient?

craggy bridge Jul 7, 2023, 9:51 PM

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The service does the following:

Run the build method from the XPTOClient(which creates a new instance of soap), this build method should run at the start of the application
Has some methods that calls the XPTOClient(which now already have the soap instance), fetch the data, parse that data and returns

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The XPTOClient is another package that i built for this specific case, which i mapped all SOAP methods available, just to let you know

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And that service will be used in many other parts of my NestJS application

junior cove Jul 7, 2023, 9:54 PM

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Wouldn't it make more sense to push the build logic to the factory? That way, you can always import a ready client

craggy bridge Jul 7, 2023, 9:54 PM

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Could you give me an example?

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Just a pseudo-code

junior cove Jul 7, 2023, 9:55 PM

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@Module({
  imports: [],
  providers: [
    {
      provide: XPTOClient,
      useFactory: async () => {
        const xptClient = new XPTOClient()
        /* do your logic */
        await xptClient.build()
        return xptoClient;
      },
    },
  ],
  exports: [XPTOClient],
})
export class XPTOModule {}

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*where you can move the factory to its own thing so you do not pollute your module

craggy bridge Jul 7, 2023, 9:55 PM

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So in this case, i would import that XPTOClient into my service?

junior cove Jul 7, 2023, 9:56 PM

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Yes and it would already be in a consumable state

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because the factory will handle it

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You can also use nest hooks to do something when the module gets initialized, up to you

craggy bridge Jul 7, 2023, 9:56 PM

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Think i got it, let me test it here

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Let me ask something, how should i import that XPTOClient into my Service? Using @Inject?

junior cove Jul 7, 2023, 10:00 PM

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up to you, if you dont care about directly injecting the client then you can just use it like so

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class Service {
  public constructor(client: XTPOClient) {}
}

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if you want to abstract it away, then the inject decorator with a custom token and an interface is an option

craggy bridge Jul 7, 2023, 10:05 PM

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Got it, i think that i'm making progress here. I applying the changes you suggested, everything is fine, but when i import my Service to another module, inside the providers:[MyService] and get an error complaining about the XPTOClient being exported by the XPTOModule

junior cove Jul 7, 2023, 10:07 PM

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Can you show me the error?

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You probably want to import the module instead of adding the service again

craggy bridge Jul 7, 2023, 10:11 PM

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Fixed here, it was missing to import XPTOClient as a provider of the module that contains the service

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No errors during the build, but when i call a method from the service, it seems that XPTOClient wasn't instantiated correctly

junior cove Jul 7, 2023, 10:12 PM

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You probably want to import the module instead

craggy bridge Jul 7, 2023, 10:14 PM

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I created a SoapModule , and added it to another Module called SharedModule, which i import it to AppModule to be available to some other methods

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I have another module, called AgencyModule that has a controller that i'm using to test that Service

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Should i import SharedModule into AgencyModule as well?

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Or import SoapModule directly?

junior cove Jul 7, 2023, 10:20 PM

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eh t hats too much information for my brain to handle at this time, sounds like you just created a circular dependency

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Is your shared module global?

craggy bridge Jul 7, 2023, 10:21 PM

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Sorry to bother you with all that information 🤷‍♂️

junior cove Jul 7, 2023, 10:21 PM

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if its not global, then its not going to pass it to the next child the way you think it would

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you would have to explicitly import shared inside the module where its needed

craggy bridge Jul 7, 2023, 10:22 PM

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My shared module is just imported into my AppModule imports array

junior cove Jul 7, 2023, 10:24 PM

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Eh, give me a second I think I messed up

craggy bridge Jul 7, 2023, 10:27 PM

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I think i fixed it. I added a @Global decorator to my SharedModule,and on my AgencyModule its compiling without any errors

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Now i'm getting an Axios error, which is probably not related to this

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I'll think on how to fix it

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I don't know if it is related, but my Service is being initialized by NestJS before my SoapModule which creates the SOAP instance inside the useFactory

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My SoapModule is taking ~1s to initialize

junior cove Jul 7, 2023, 10:32 PM

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Okay so what I told you was correct, just re created it to make sure im not going insane. e.g. this works. I'm not a big fan of importing the module in shared and shared in Y and Z but alright

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whats your next problem

craggy bridge Jul 7, 2023, 10:34 PM

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My Service,which uses that XPTOClient, relies on the useFactory inside my SoapModule

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The module that has the service, gets initialized waay before my SoapModule(which is taking 1s)

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So when i call the service methods, i'm getting an Axios error, which seems to be related to the SOAP client that wasn't initialized as expected

junior cove Jul 7, 2023, 10:36 PM

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Why is the service not in the same module though? Aren't they related?

craggy bridge Jul 7, 2023, 10:36 PM

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I thought they should be separated, according to your examples 🥲

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Let me merge them

junior cove Jul 7, 2023, 10:37 PM

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Code that belongs together should be together ^^

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just to give you a visual on what I have

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anyway I hope this is enough to get you forward, Im desperate for sleep

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had 4 hours last night and its already 00:40 here, cheers!

craggy bridge Jul 7, 2023, 10:40 PM

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Have a good night!

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And thanks for all your help

#Dynamic Module async