How to solve the circular dependency

Question

I have 3 services:

auth.service.ts, account.service.ts, http.service.ts

While user signup I should create new account therefore I imported account.service.ts to auth.service.ts. I should do it because I use signup form data for creating a new account.

@Injectable() export class AuthService {   constructor(public accountService: AccountService) {}    signUp(name: string, phone: string, email: string, password: string): void {      ...    userPool.signUp(phone, password, attributeList, null, (err: any, result: any) => {   if (err) {      ...      return;   }    this.accountService.createAccount(name, phone, email).subscribe(res => {      ...      this.router.navigate(['/auth/confirmation-code']);   }); }); 

}

So as I use AWS Cognito I should add an authorization token from auth.service.ts to http.service.ts therefore I imported auth.service.ts to http.service.ts.

@Injectable() export class HttpService {   private actionUrl: string;   private headers: Headers;   private options: RequestOptions;    constructor(     public _http: Http,     public authService: AuthService    ) {     this.actionUrl = 'https://example.com/dev';     this.headers = new Headers();      this.authService.getAuthenticatedUser().getSession((err: any, session: any) => {       if(err) return;       this.headers.append('Authorization', session.getIdToken().getJwtToken());     });      this.headers.append('Content-Type', 'application/json');     this.headers.append('Accept', 'application/json');     this.headers.append('Access-Control-Allow-Headers', 'Content-Type, X-XSRF-TOKEN');     this.headers.append('Access-Control-Allow-Origin', '*');      this.options = new RequestOptions({ headers: this.headers });   }      get(request: string): Observable<any> {         return this._http.get(`${this.actionUrl}${request}`)             .map(res => this.extractData(res))             .catch(this.handleError);    } 

In my account.service.ts I should use http.service.ts for creating new account.

@Injectable() export class AccountService {   constructor(public httpService: HttpService) {} 

WARNING in Circular dependency detected: src/app/core/services/account.service.ts -> src/app/core/services/http.service.ts -> src/app/core/services/auth.service.ts -> src/app/core/services/account.service.ts

WARNING in Circular dependency detected: src/app/core/services/auth.service.ts -> src/app/core/services/account.service.ts -> src/app/core/services/http.service.ts -> src/app/core/services/auth.service.ts

WARNING in Circular dependency detected: src/app/core/services/http.service.ts -> src/app/core/services/auth.service.ts -> src/app/core/services/account.service.ts -> src/app/core/services/http.service.ts

I understand that this is circular dependency Error. How to solve it? Best practice? All services fulfill their role and are important.

Answer 1

You can use Injector for this. Inject it via constructor as usual, and then when you will need some service that leads to the circular dependency, get that service from it.

class HttpService {   constructor(private injector: Injector) { }    doSomething() {     const auth = this.injector.get(AuthService);     // use auth as usual   } }