循环依赖注入 angular 2

Question

我一直在努力将 services 注入彼此。下面的博客 Circular Dependency in constructors and Dependency Injection 写的

有点让人困惑

One of the two objects is hiding another object C

我在将服务 class 相互注入时出现以下错误

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);
   }
}

非常感谢您的评论和回答。

谢谢

Answer 1

您可以通过注入 Injector 而不是导致循环依赖的服务之一来解决循环依赖

private payrollService:PayrollService;
constructor(/*private payrollService:PayrollService*/ injector:Injector) {
  setTimeout(() => this.payrollService = injector.get(PayrollService));
}

Answer 2

在我的例子中（Angular 4 在一个 Ionic 项目中）甚至在它被使用之前（在用户交互时）注入服务也不起作用（在启动时相同 "Can't resolve all parameters..."）。

对我有用的是按名称注入（并因此提供）服务。

所以在我的应用程序模块中：

...
providers: [{provide: "MyServiceName", MyServiceClass}],
...

需要时：

const myService: MyServiceClass = injector.get("MyServiceName");
...

Answer 3

我知道 post 已经过时了，但还是感谢上面的解决方案对我有用，因为我有循环依赖问题，所以我必须使用注入器来避免创建中介服务来进行通信，尽管上面的解决方案中有一个更正

从Angular5开始我们需要使用：

提供者：[{提供："MyServiceName"，使用类： MyServiceClass}]，

然后

injector.get('MyServiceName')

虽然 get 被破坏了

循环依赖注入 angular 2

Circular dependency injection angular 2

dependency-injection

circular-dependency

angular