从父组件获取子级窗体。$invalid

import { Component } from '@angular/core';
import { NgForm } from '@angular/forms';

@Component({
  selector: 'app-child',
  template: `
    <form #myForm="ngForm">
      <input type="text" name="name" ngModel required>
    </form>
  `
})
export class ChildComponent {
  // ...
}

import { Component, ViewChild } from '@angular/core';
import { ChildComponent } from './child.component';

@Component({
  selector: 'app-parent',
  template: `
    <app-child></app-child>
    <button (click)="checkFormValidity()">Check Form Validity</button>
  `
})
export class ParentComponent {
  @ViewChild(ChildComponent) childComponent: ChildComponent;

  checkFormValidity() {
    console.log(this.childComponent.myForm.form.invalid);
  }
}