Angular component 没有constructor如何调用service

Add this code in app.module.ts

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

export let AppInjector: Injector;
    
export class AppModule {
  constructor(private injector: Injector) {
    AppInjector = this.injector;
  }
}

然后在你的component中引入

import { AppInjector } from '../app.module';

const myService = AppInjector.get(MyService);