Trigger an event from a component to an invisible component in Angular 5

Question

I have a div inside a component (child.html) and I would trigger a click event to the another (parent.html) to turn a boolean from false to true. I know it is possible using html as <child-component [Event]></child-component> but the child have to be invisible to the user.

Is it possible to add CSS to from the app.css to make it invisible? I am not sure if it is possible to make it in Angular, here is what I tried:

child.html:

   <div class="notif-filter" (click)="hideNotif(event)"> </div>

child.ts:

 public hideNotif(event) {
    console.log(event, 'hideNotif is fired !!');
     this.hideMe = true;
    // this.feedIsVisible = false;
   }

parent.html: (this one should be invisible)

  <child-component></child-component> 

parent.css:

 app-child: { display: none }

parent.ts:

     @input event: Event (comming from the child)

    lockScreen(): void {
    this.screenLocked = true;
    this.feedIsVisible = false;    ==> *This should turn to true depending on 
    the click event in the child.html*
    this.nav.setRoot('ConnexionPage').then();
  }

Answer 1

First read about Angular Component Interaction .

Then you will know that there are 4 main ways to communicate between components.

• Pass data from parent to child with input binding
• Parent listens for child event
• Parent interacts with child via local variable
• https://angular.io/guide/component-interaction#parent-and-children-communicate-via-a-service .

In your scenario you can use any method you want.

look at this example

child.component.ts

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

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

  @Output()
  public childButtonClick = new EventEmitter<boolean>();

  constructor() {
    this.show = true;
  }

  public onClick(): void {
    this.show = !this.show;
    this.childButtonClick.emit(this.show);
  }

}

child.component.html

<button (click)="onClick()">Child button</button>

app.component.ts

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

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  public show: boolean;


  constructor() {
    this.show = true;
  }
  public onChildButtonClick(value): void {
    this.show = value;
  }
}

app.component.html

<app-child (childButtonClick)="onChildButtonClick($event)"></app-child>


<div *ngIf="show">
  This will be hidden when you click the button
  And I'm using ngIf directive
</div>

<br>
<br>

<div [ngClass]="{'hide-me': !show}">
  This will be hidden when you click the button
  And I'm using ngClass directive
</div>

<br>
<div>
  show value: {{show}}
</div>

app.component.css

.hide-me {
  display: none
}

In here I've used the Parent listens for child event method. And I've created a stackblitz for this.

Answer 2

Working Example

HTML:

hello.componemt.html

<button (click)="onClick()">hello button</button>

app.component.html

<hello (childClick)="onChildButtonClick($event)"></hello>

{{show}}

TS:

hello.component.ts:

import { Component,Input, Output, EventEmitter, } from '@angular/core';

@Component({
 selector: 'hello',
  templateUrl: './hello.component.html',
  styleUrls: [ './app.component.css' ]
})
export class HelloComponent  {

  public show: boolean;

  @Output()
  public childClick = new EventEmitter<boolean>();

  constructor() {
    this.show = true;
  }

  public onClick(): void {
    this.show = !this.show;
    this.childClick.emit(this.show);
  }
}

app.component.ts:

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

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular 6';
   public show: boolean;


  constructor() {
    this.show = true;
  }
  public onChildButtonClick(value): void {
    this.show = value;
  }
}