I've been struggling around injecting services
into each other. The following blog Circular Dependency in constructors and Dependency Injection is kind of confusing where it says
One of the two objects is hiding another object C
I get the following error while injecting Service class into each other
Can't resolve all parameters for PayrollService: (SiteService, StorageService, SweetAlertService, ?)
//abstractmodal.service.ts
@Injectable()
export abstract class AbstractModel {
abstract collection = [];
constructor(private siteService: SiteService, private storageService: StorageService,
private sweetalertService: SweetAlertService) {}
setCollectionEmpty() {
this.collection = [];
}
}
//account-payable.service.ts
@Injectable()
export class AccountPayableService extends AbstractModel {
public collection = [];
constructor(private sS: SiteService,private stS: StorageService, private sws: SweetAlertService,
private accpPoService: PayablePurchaseOrderService, private attachmentService: AttachmentService,
private injectorService: InjectorService) {
super(sS, stS, sws);
}
}
//injector.service.ts
@Injectable()
export class InjectorService {
constructor(private payrollService: PayrollService) {}
cleanPayrollCollection() {
this.payrollService.setCollectionEmpty();
}
}
//payroll.service.ts
@Injectable()
export class PayrollService extends AbstractModel {
public collection = [];
constructor(private sS: SiteService,private stS: StorageService, private sws: SweetAlertService,
private accpService: AccountPayableService) {
super(sS, stS, sws);
}
}
Your comments and answered will be appreciated a lot.
Thanks
In my case (Angular 4 in an Ionic project) even injecting the service just before it's usage (upon user interaction) was not working (Same "Can't resolve all parameters..." at startup).
What worked for me was to inject (and thus provide) the service by name.
So in my app module :
And when needed :
You can workaround circular dependencies by injecting
Injector
instead of one of the services that cause the circular dependencyI know the post is old but thanks anyways above solution has worked for me as i had cyclic dependency problem so i have to use injector to avoid creating mediator service to communicate, Although one correction in above solution
From Angular 5 onwards we need to use:
providers: [{provide: "MyServiceName",useclass: MyServiceClass}],
and then
injector.get('MyServiceName')
although get is derpecated