TypeScript中的Property has no initializer错误：如何修复？

大家好！我是TypeScript和Angular的新手，遇到了一个非常奇怪的错误。我有一个组件，在其中声明了一个属性，但TypeScript报错说它没有初始化。这是我的代码： ```typescript import { Component, Input } from '@angular/core'; @Component({ selector: 'app-user', template: ` ` }) export class UserComponent { @Input() user: User; public userName: string; private id: number; constructor() { // 在构造函数中什么都不做 } ngOnInit() { this.userName = this.user.name; this.id = this.user.id; } } ``` 编译时我收到以下错误： - `Property 'user' has no initializer and is not definitely assigned in the constructor.` - `Property 'userName' has no initializer and is not definitely assigned in the constructor.` - `Property 'id' has no initializer and is not definitely assigned in th