Inject a service requiring constructor parameter

There is an official way that Angular team recommends in here. It basically allows you to inject statically typed configuration classes.

I have successfully implemented it and here is all the relevant code:

1) app.config.ts

import { OpaqueToken } from "@angular/core";export let APP_CONFIG = new OpaqueToken("app.config");export interface IAppConfig {    apiEndpoint: string;}export const AppConfig: IAppConfig = {        apiEndpoint: "http://localhost:15422/api/"    };

2) app.module.ts

import { APP_CONFIG, AppConfig } from './app.config';@NgModule({    providers: [        { provide: APP_CONFIG, useValue: AppConfig }    ]})

3) your.service.ts

import { APP_CONFIG, IAppConfig } from './app.config';@Injectable()export class YourService {    constructor(@Inject(APP_CONFIG) private config: IAppConfig) {             // You can use config.apiEndpoint now    }   }

Now you can inject the config everywhere without using the string names and with the use of your interface for static checks.

You can of course separate the Interface and the constant further to be able to supply different values in production and development e.g.

The above answer has been deprecated since angular 4Now you can use it like this:

import { NgModule, APP_INITIALIZER } from '@angular/core';@NgModule({  providers: [    {      provide: APP_INITIALIZER,      useFactory: onAppInit1,      multi: true,      deps: [/* your dependencies */]    },    {      provide: APP_INITIALIZER,      useFactory: onAppInit2,      multi: true,      deps: [/* your dependencies */]    }  ]})export class AppModule { }

You can use @Inject, explained here

In your service:

import {Inject, Injectable} from '@angular/core';@Injectable({  providedIn: 'root'})export class NgService {    constructor (       @Inject('paramId') private paramId: string    ) { }}

And then, in your component:

import { Component } from '@angular/core';@Component({  selector: 'app-demo',  template: `    <div"> </div>  `,   providers: [    {provide: 'paramId', useValue: 'param-id'},  ]})export class AppComponent {  constructor(private ngService: NgService) { }}