使Angular服务对所有组件可用

import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-my-component',
  template: `
    <div>{{ dataService.getData() }}</div>
  `,
})
export class MyComponent {
  constructor(private dataService: DataService) {}
}

import { NgModule } from '@angular/core';
import { DataService } from './data.service';

@NgModule({
  providers: [DataService],
})
export class MyModule {}

import { NgModule } from '@angular/core';
import { DataService } from './data.service';

@NgModule({
  providers: [DataService],
})
export class AppModule {}