角度2喷油器错误＆＃34;无法读取属性＆＃39;实例＆＃39;未定义＆＃34;

Question

我使用值提供程序使用此组件：

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");
 }
}

当我运行程序时，进样器会抛出一个错误，＆＃34; Cannot read property 'instance' of undefined＆＃34;

如果重要，我的观点很简单<h1>{{title}}</h1>。

我做错了什么？

Answer 1

不要使用Injector，只需导入'Inject'装饰器并使用如此 -

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;
  }
}