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How to access dynamically injected service in root component - Angular 2

I am writing a browser extension that has different services for Firefox and Chrome. The proper version of each service needs to be injected depending on the environment variable. While I can properly inject the appropriate service in the AppModule, I am unsure of how to get the proper services in my root component without a hacky workaround.

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './index';
import { environment } from '../environments/environment';
import { MessageService } from './messaging.service';
import { MessageServiceFirefox } from './ff.messaging.service';
import { ScreenshotService } from './screenshot.service';
import { ScreenshotServiceFirefox } from './ff.screenshot.service';

export function screenshotFactory() {
  if (environment.envName == 'prod-ff' || environment.envName == 'ff') {
    return new ScreenshotServiceFirefox();
  } else {
    return new ScreenshotService();
  }
}

export function messageFactory() {
  if (environment.envName == 'prod-ff' || environment.envName == 'ff') {
    return new MessageServiceFirefox();
  } else {
    return new MessageService();
  }
}

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
  ],
  providers: [
    {
      provide: ScreenshotService,
      useFactory: screenshotFactory
    },
    {
      provide: MessageService,
      useFactory: messageFactory
    }
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.component.ts

import { Component } from '@angular/core';
import { ScreenshotService } from './screenshot.service';
import { MessageService } from './messaging.service';
// Would need to import ScreenshotServiceFirefox and MessageServiceFirefox
// and have conditional logic to establish correct ScreenshotService and MessageService

@Component({
  moduleId: module.id,
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
  providers: [ScreenshotService, MessageService]
})


export class AppComponent {
  constructor(private screenshotService: ScreenshotService, private messageService: MessageService) {}

  takeScreenshot (){
    this.messageService.injectScript()
      .then(this.screenshotService.takeScreenshot)
      .then(this.screenshotService.convertToBlob)
      .then(this.screenshotService.downloadLocally)
  }
}

I've also tries using solutions here, here and here but none deal with accessing the injected service from within the root component without using the same conditional logic.

I'm open to suggestions of other ways to achieve this.

over 4 years ago · Santiago Trujillo
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