Angular service keeps saying NullInjectorError: No provider for anotherService-CodePudding

I created simple angular service

@Injectable()

export class someHandler {

    constructor(
        public anotherService: anotherService,
    ) {}
...

Problem is that when I use this service in some component it keeps saying that NullInjectorError: No provider for anotherService but I cant use providers: [] inside service right? So what can I do? Thanks for any help.

CodePudding user response：

Not sure because you didn't provide the module.ts but looks like anotherService is not part of the same module as someHandler.

In the module where you defines providers : ['someHandler']

You must import the module that include anotherService -> imports: [..., anotherServiceModule]

CodePudding user response：

We must tell Angular to instantiate AnotherService to be available (instatiated) before SomeHandler. So in your module:

@NgModule({
  declarations: [
    AppComponent,
    Component1Component
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule
  ],
  providers: [AnotherService],
  bootstrap: [AppComponent]
})
export class AppModule { }

Like this, AnotherService is provided to the entire application as singleton and it is already instantiated.