Angular DI: Injecting a value token into factory provider

问题

Is it possible to inject an InjectionToken into a factory provider:

Currently, I've coded that:

export const HOST_TOKEN = new InjectionToken<string>("host");

let configDataServiceFactory = (userService: UserService, host: string) => {
    return new Config("host", 8080, userService.getUser(), userService.getPasswd());
};

export let configDataServiceProvider =
{
    provide: CONFIG_API,
    useFactory: configDataServiceFactory,
    deps: [UserService, HOST_TOKEN]
};

Into my module:

@NgModule(
  providers: [
    {provide: HOST_TOKEN, useValue: "allianz-host"},
    configDataServiceProvider
  ]
)

Nevertheless, angular is injecting on configDataServiceProvider value "host", instead of "host-allianz"

Any ideas?

回答1:

Yes, you can do that using @Inject decorator like below, which will help you to extract the relevant dependency from DI container.

let configDataServiceFactory = (userService: UserService, @Inject(HOST_TOKEN) host: string) => {
    return new Config(host, 8080, userService.getUser(), userService.getPasswd());
};

You can also consider below option as well. Basically all registered InjectionToken's would be available to retrieve from application Injector, that can be achieve by calling get method over injector instance and pass InjectorToken name.

export const HOST_TOKEN = new InjectionToken<string>("host");

let configDataServiceFactory = (userService: UserService, injector: Injector) => {
    let host = injector.get(HOST_TOKEN); //retrieved token from injector
    return new Config(host, 8080, userService.getUser(), userService.getPasswd());
};

export let configDataServiceProvider =
{
    provide: CONFIG_API,
    useFactory: configDataServiceFactory,
    deps: [UserService, Injector]
};

Docs Here

来源：https://stackoverflow.com/questions/50742028/angular-di-injecting-a-value-token-into-factory-provider

标签

angular

typescript

dependency-injection