Angular 2 injector error "Cannot read property 'instance' of undefined"

Question

I have this component using a value provider:

import { Component, OnInit, Injector } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
  providers: [{
    provide: "currency",
    useValue : "dollar"
  }]
})
export class AppComponent implements OnInit  {
  ngOnInit(): void {

  }

title = "app works";


constructor(private injector: Injector){
 this.title = "Currency is: "+ injector.get("currency");
 }
}

When I run the program, the injector throws an error saying, "Cannot read property 'instance' of undefined"

If it matters, my view is a simple <h1>{{title}}</h1>.

What I'm I doing wrong?

Answer 1

Don't use Injector, just import the 'Inject' decorator and use like so-

import { Component, OnInit, Inject } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
  providers: [{
     provide: "currency",
     useValue : "dollar"
  }]
})
export class AppComponent implements OnInit  {
  ngOnInit(): void {

  }

  title = "app works";


  constructor(@Inject("currency") private currency){
     this.title = "Currency is: "+ currency;
  }
}