Angular 7 : Injected service is undefined

Question

I tried to inject AccountService in the LoginService but it won\'t ,the accountService is undefined but in the other hand the authServiceProvider is defined .

Contraril

Answer 1

HttpClientModule is required for HttpClient. Just import in AppModule.

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { CoreModule } from './core/core.module';
import { HttpClientModule } from '@angular/common/http';
import { MatTreeModule } from '@angular/material';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    AppRoutingModule,
    CoreModule,
    MatTreeModule,
    FormsModule,
    ReactiveFormsModule,
    HttpClientModule //add this as fix, simple
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Answer 2

The same thing happened to me, the solution was the one mentioned by the user span

-> Passing arrow function instead of regular function in the callback. Arrow functions don't have its own this.

Difference between regular functions and arrow functions here

Answer 3

You should always provide your service in the root injector unless there is a case where you want the service to be available only if the consumer imports a particular @NgModule.

try to add your service you want to inject in providers : [ ] in your core.module

import { NgModule, LOCALE_ID } from '@angular/core';
import { DatePipe, registerLocaleData } from '@angular/common';
import { HttpClientModule } from '@angular/common/http';
import { Title } from '@angular/platform-browser';
import locale from '@angular/common/locales/en';
@NgModule({
    imports: [HttpClientModule],
    exports: [],
    declarations: [],
    providers: [
        AccountService,
        Title,
        {
            provide: LOCALE_ID,
            useValue: 'en'
        },
        DatePipe
    ]
})
export class CoreModule {
    constructor() {
        registerLocaleData(locale);
    }
}

and in your AccountService replace @Injectable({ providedIn: 'root' }) with @Injectable()

@Injectable()
export class AccountService {
    private userIdentity: any;
    private authenticated = false;
    private authenticationState = new Subject<any>();
    constructor(private languageService: JhiLanguageService, private sessionStorage: SessionStorageService, private http: HttpClient) {}