Hierarchical injector about nest

[kamilmysliwiec]

Hi @AurelieV,
I made a set of improvements for a dependency injector, so now your example should works fine. Please, update your packages (since ~2.* version @nestjs/core, @nestjs/common etc.) into latest versions.

[AurelieV]

The problem is I do not want my two modules being dependant on each others.
AuthenticationService can be use without UserModule.
UserService is not part of UserModule

[cojack]

@AurelieV try:

@Module({
    modules: [ UserModule ], 
    controllers: [],
    components: [ AuthenticationService ],
    exports: [ 
        AuthenticationService
    ]
})
class AuthenticationModule {}

as it's described here: https://kamilmysliwiec.gitbooks.io/nest/content/advanced/shared-module.html

[AurelieV]

An other example will be to inject Configuration class, and re-use your modules accross different applications. You inject the app-specific configuration on app module decorator, you import the different modules and everything will be working for this app.

[kamilmysliwiec]

Hi @AurelieV,
The problem is that modules in Nest are a singletons, so it is possible to share same instances between them using some kind of shared module. Hierarchical injection in this case makes impossible to share components across e.g. two modules. What you show is definitely needed and I'll make it supported as soon as possible, but it could reflect on shared modules mechanism. It seems we need another feature, which allows to mark modules as shared / singletons. Scope also should be possible to set.

[AurelieV]

Yep.
Will also be greet to import module into other with only components, and not controllers (equivalent to forRoot and forChild in angular)

[lock]

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