从父类调用子组件方法-Angular

Question

我已经创建了一个子组件，它有一个我想调用的方法。

当我调用这个方法时，它只触发console.log（）行，它不会设置test属性？？

下面是快速启动的Angular应用程序和我的更改。

家长

import { Component } from '@angular/core';
import { NotifyComponent }  from './notify.component';

@Component({
    selector: 'my-app',
    template:
    `
    <button (click)="submit()">Call Child Component Method</button>
    `
})
export class AppComponent {
    private notify: NotifyComponent;

    constructor() { 
      this.notify = new NotifyComponent();
    }

    submit(): void {
        // execute child component method
        notify.callMethod();
    }
}

孩子

import { Component, OnInit } from '@angular/core';

@Component({
    selector: 'notify',
    template: '<h3>Notify {{test}}</h3>'
})
export class NotifyComponent implements OnInit {
   test:string; 
   constructor() { }

    ngOnInit() { }

    callMethod(): void {
        console.log('successfully executed.');
        this.test = 'Me';
    }
}

如何设置test属性？

Answer 1

这对我有用！对于Angular 2，在父组件中调用子组件方法

父组件

    import { Component, OnInit, ViewChild } from '@angular/core';
    import { ChildComponent } from '../child/child'; 
    @Component({ 
               selector: 'parent-app', 
               template: `<child-cmp></child-cmp>` 
              }) 
    export class parentComponent implements OnInit{ 
        @ViewChild(ChildComponent ) child: ChildComponent ; 

        ngOnInit() { 
           this.child.ChildTestCmp(); } 
}

子组件

import { Component } from '@angular/core';
@Component({ 
  selector: 'child-cmp', 
  template: `<h2> Show Child Component</h2><br/><p> {{test }}</p> ` 
})
export class ChildComponent {
  test: string;
  ChildTestCmp() 
  { 
    this.test = "I am child component!"; 
  }
 }

Answer 2

我认为最简单的方法是使用Subject。在下面的示例代码中，每次调用“tellChild（）”时都会通知孩子。

父组件

import {Subject} from 'rxjs/Subject';
...
export class ParentComp {
  changingValue: Subject<boolean> = new Subject();
        
  tellChild() {
    this.changingValue.next(true);
  }
}

Parent.component.html

<my-comp [changing]="changingValue"></my-comp>

子组件

...
export class ChildComp implements OnInit{
  @Input() changing: Subject<boolean>;
  
  ngOnInit(){
    this.changing.subscribe(v => { 
      console.log('value is changing', v);
    });
  }
}

Stackblitz上的工作样本

Answer 3

您可以使用@ViewChild了解更多信息，请查看此链接

带类型选择器

子组件

@Component({
  selector: 'child-cmp',
  template: '<p>child</p>'
})
class ChildCmp {
  doSomething() {}
}

父组件

@Component({
  selector: 'some-cmp',
  template: '<child-cmp></child-cmp>',
  directives: [ChildCmp]
})
class SomeCmp {

  @ViewChild(ChildCmp) child:ChildCmp;

  ngAfterViewInit() {
    // child is set
    this.child.doSomething();
  }
}

带字符串选择器

子组件

@Component({
  selector: 'child-cmp',
  template: '<p>child</p>'
})
class ChildCmp {
  doSomething() {}
}

父组件

@Component({
  selector: 'some-cmp',
  template: '<child-cmp #child></child-cmp>',
  directives: [ChildCmp]
})
class SomeCmp {

  @ViewChild('child') child:ChildCmp;

  ngAfterViewInit() {
    // child is set
    this.child.doSomething();
  }
}