使用 Angular 类构造函数来获取依赖项

在旧的类型脚本中，属性的初始化在幕后移到构造函数代码的开头.

在ES2022中，属性的初始化是在构造函数中完成的，而不是在构造函数中.

所以你的例子没有区别，甚至

export class ExampleComponent {
  private service = inject(Dependency);
  private widget = this.service.getWidget();
}

和

export class ExampleComponent {
  private service: Dependency;
  private widget;

  constructor( ) { 
    this.service = inject(Dependency);
    this.widget = this.service.getWidget();
  }
}

是面向future 的，但

export class ExampleComponent {
  private widget = this.service.getWidget();

  constructor(private service: Dependency) {}
}

将来可能不会工作，但它今天可以工作，因为TypeScrip当前初始化widget-inside构造函数.

As a rule, I set up observables in the constructor, but observers in ngOnInit. The way I think of it, observables are just plumbing. Until subscribed to, nothing is flowing. In contrast, before you subscribe or otherwise add an observer your component must be set up 和 ready to go! This helps avoid bugs where the code is waiting for a value that was streamed/emitted before all the plumbing was in place.