Angular，如何为两个字段中的任何一个设置验证，应在反应表单方法中验证

import { Component } from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';

@Component({
  selector: 'app-example',
  template: `
    <form [formGroup]="myForm" (ngSubmit)="onSubmit()">
      <input type="text" formControlName="field1">
      <input type="text" formControlName="field2">
      <button type="submit">Submit</button>
    </form>
  `
})
export class ExampleComponent {
  myForm: FormGroup;

  constructor() {
    this.myForm = new FormGroup({
      field1: new FormControl('', Validators.required),
      field2: new FormControl('', Validators.required)
    });
  }

  onSubmit() {
    if (this.myForm.valid) {
      // 执行提交操作
    }
  }
}

function validateEitherField(control: FormGroup): { [key: string]: boolean } | null {
  const field1Value = control.get('field1').value;
  const field2Value = control.get('field2').value;

  if (!field1Value && !field2Value) {
    return { eitherFieldRequired: true };
  }

  return null;
}

this.myForm = new FormGroup({
  field1: new FormControl('', Validators.required),
  field2: new FormControl('', Validators.required)
}, { validators: validateEitherField });