Angular - 以构造函数以外的其他方式注入(inject)？

Question

在 Angular 中，我有一个服务，它通过 constructor(...) 注入(inject)了一些东西。然而，该服务也在某个地方通过调用构造函数创建。因此，将它所依赖的另一个服务添加到参数中会更改 API。我想避免这种情况。

有没有办法在不将服务添加到构造函数参数的情况下将服务注入(inject)另一个服务？例如。字段注入(inject)？

import {Inject, Injectable} from "@angular/core";
import {
    Http, Request, ConnectionBackend, RequestOptions, RequestOptionsArgs, Response, Headers,
    RequestMethod
} from "@angular/http";

import {KeycloakService} from "./keycloak.service";
import {Observable} from 'rxjs/Observable';
import {EventBusService} from "../events/event-bus.service";
import {LoadingSomethingFinishedEvent, LoadingSomethingStartedEvent} from "../events/windup-event";

@Injectable()
export class WindupHttpService extends Http {
    constructor(
        _backend: ConnectionBackend,
        _defaultOptions: RequestOptions,
        private _keycloakService: KeycloakService,
        // ----- This is what I want to avoid. -----
        private _eventBus: EventBusService,
    ) {
        super(_backend, _defaultOptions);
    }

    // -------  This is what I am looking for ---------
    //@Inject()
    //private _eventBus: EventBusService;

Answer 1

是也不是。

您可以使用Injector，但最好的方法是将其注入(inject)到服务中:

constructor(private injector: Injector) {
        let httpService: Http = this.injector.get(Http);
}

可在此处找到有关 Injector 的更多信息: https://angular.io/api/core/Injector

正如@DBosley 提到的，这里也是可用的链接:https://angular.io/guide/dependency-injection#appendix-working-with-injectors-directly