角2喷油器错误“无法读取的未定义的属性‘实例’”

Question

我有利用价值提供这个组件：

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"); 
} 
} 

当我运行该程序时，注入引发错误的说法，“Cannot read property 'instance' of undefined”

如果重要，我的看法是一个简单的<h1>{{title}}</h1>。

我做错了什么？

Answer 1

不要使用注射器，只是导入“进样”的装饰，并使用像所谓

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; 
    } 
}