Call child component method from parent class - Angular

You can do this by using @ViewChild for more info check this link

With type selector

child component

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

parent component

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

  @ViewChild(ChildCmp) child:ChildCmp;

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

With string selector

child component

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

parent component

@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();
  }
}

---

I think most easy way is using Subject. In below example code, the child will be notified each time 'tellChild()' is called.

Parent.component.ts

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>

Child.component.ts

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

Working sample on Stackblitz

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This Worked for me ! For Angular 2 , Call child component method in parent component

Parent.component.ts

    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(); } 
}

Child.component.ts

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!"; 
  }
 }

---

Angular – Call Child Component’s Method in Parent Component’s Template

You have ParentComponent and ChildComponent that looks like this.

parent.component.html

https://i.stack.imgur.com/40D0r.png

parent.component.ts

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

@Component({
  selector: 'app-parent',
  templateUrl: './parent.component.html',
  styleUrls: ['./parent.component.css']
})
export class ParentComponent {
  constructor() {
  }
}

child.component.html

<p>
  This is child
</p>

child.component.ts

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

@Component({
  selector: 'app-child',
  templateUrl: './child.component.html',
  styleUrls: ['./child.component.css']
})
export class ChildComponent {
  constructor() {
  }

  doSomething() {
    console.log('do something');
  }
}

When serve, it looks like this:

https://i.stack.imgur.com/rnywq.png

When user focus on ParentComponent’s input element, you want to call ChildComponent’s doSomething() method.

Simply do this:

Give app-child selector in parent.component.html a DOM variable name (prefix with # – hashtag), in this case we call it appChild. Assign expression value (of the method you want to call) to input element’s focus event.

https://i.stack.imgur.com/jixZC.png

The result:

https://i.stack.imgur.com/qC1Cg.gif

---

user6779899's answer is neat and more generic However, based on the request by Imad El Hitti, a light weight solution is proposed here. This can be used when a child component is tightly connected to one parent only.

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 
        };
    }
 }

---

Consider the following example,

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();
    }
}

Read more about @ViewChild here.

---

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
    }
}

---

I had an exact situation where the Parent-component had a Select element in a form and on submit, I needed to call the relevant Child-Component's method according to the selected value from the select element.

Parent.HTML:

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

Parent.TS:

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

Child.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(){ }
}

Hope this helps.

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