从父类- Angular调用子组件方法

我已经创建了一个子组件，其中有一个我想调用的方法。

当我调用这个方法时，它只会触发console.log()行，它不会设置测试属性??

下面是我修改后的Angular快速入门应用。

父

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';
    }
}

我如何设置测试属性以及?

当前回答

我有一个确切的情况，父组件在表单中有一个Select元素，在提交时，我需要根据从选择元素中选择的值调用相关的子组件的方法。

Parent.HTML:

<form (ngSubmit)='selX' [formGroup]="xSelForm">
    <select formControlName="xSelector">
      ...
    </select>
<button type="submit">Submit</button>
</form>
<child [selectedX]="selectedX"></child>

的父母。TS:

selX(){
  this.selectedX = this.xSelForm.value['xSelector'];
}

的孩子。TS:

export class ChildComponent implements OnChanges {
  @Input() public selectedX;

  //ngOnChanges will execute if there is a change in the value of selectedX which has been passed to child as an @Input.

  ngOnChanges(changes: { [propKey: string]: SimpleChange }) {
    this.childFunction();
  }
  childFunction(){ }
}

希望这能有所帮助。

2020-05-30 17:53:41

其他回答

parent.component.html

<app-child #childComponent></app-child>

parent.component.ts

@Component({
    selector: 'app-parent',
    templateUrl: './app-parent.component.html',
    styleUrls: ['./app-parent.component.scss']
})
export class ParentComponent {
    @ViewChild('childComponent', {static: false}) childComponent: ChildComponent;

    anyMethod(): void {
        childComponent.updateData() // updateData is a child method
    }
}

child.component.ts

@Component({
    selector: 'app-child',
    templateUrl: './app-child.component.html',
    styleUrls: ['./app-child.component.scss']
})
export class ChildComponent {
    updateData(): void {
      // Method code goes here
    }
}

2021-11-26 11:19:13

考虑下面的例子:

import import { AfterViewInit, ViewChild } from '@angular/core';
import { Component } from '@angular/core';
import { CountdownTimerComponent }  from './countdown-timer.component';

@Component({
    selector: 'app-countdown-parent-vc',
    templateUrl: 'app-countdown-parent-vc.html',
    styleUrl: [app-countdown-parent-vc.css]
})
export class CreateCategoryComponent implements OnInit, AfterViewInit {
    @ViewChild(CountdownTimerComponent, {static: false}) private timerComponent: CountdownTimerComponent;
    ngAfterViewInit() {
        this.timerComponent.startTimer();
    }

    submitNewCategory(){
        this.ngAfterViewInit();
    }
}

点击这里阅读更多关于@ViewChild的信息。

2019-11-02 11:33:32

我有一个确切的情况，父组件在表单中有一个Select元素，在提交时，我需要根据从选择元素中选择的值调用相关的子组件的方法。

Parent.HTML:

<form (ngSubmit)='selX' [formGroup]="xSelForm">
    <select formControlName="xSelector">
      ...
    </select>
<button type="submit">Submit</button>
</form>
<child [selectedX]="selectedX"></child>

的父母。TS:

selX(){
  this.selectedX = this.xSelForm.value['xSelector'];
}

的孩子。TS:

export class ChildComponent implements OnChanges {
  @Input() public selectedX;

  //ngOnChanges will execute if there is a change in the value of selectedX which has been passed to child as an @Input.

  ngOnChanges(changes: { [propKey: string]: SimpleChange }) {
    this.childFunction();
  }
  childFunction(){ }
}

希望这能有所帮助。

2020-05-30 17:53:41

你可以使用@ViewChild来查看更多信息

使用类型选择器

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();
  }
}

使用字符串选择器

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();
  }
}

2016-08-16 12:27:52

User6779899的答案简洁且更通用但是，根据Imad El Hitti的要求，这里提出了一种轻量级的解决方案。当子组件仅与一个父组件紧密连接时，可以使用此选项。

Parent.component.ts

export class Notifier {
    valueChanged: (data: number) => void = (d: number) => { };
}

export class Parent {
    notifyObj = new Notifier();
    tellChild(newValue: number) {
        this.notifyObj.valueChanged(newValue); // inform child
    }
}

Parent.component.html

<my-child-comp [notify]="notifyObj"></my-child-comp>

Child.component.ts

export class ChildComp implements OnInit{
    @Input() notify = new Notifier(); // create object to satisfy typescript
    ngOnInit(){
      this.notify.valueChanged = (d: number) => {
            console.log(`Parent has notified changes to ${d}`);
            // do something with the new value 
        };
    }
 }

2019-01-28 10:54:48

从父类- Angular调用子组件方法

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