Tips for transferring an increment value from a child component to a counter in the parent component?

Having previously developed a regular Counter App in Angular, I decided to challenge myself further by creating individual components for each increment/decrement button. My goal is to update the Count in the Parent component by passing the updated increment back up. While I have successfully implemented the increment functionality in my child component, I am facing some uncertainty on how to pass this updated data back to the parent. Any guidance would be highly appreciated. Thank you.

This is the TypeScript file in the Parent component:

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

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'complicatedAngularCounter';
  currentCount:any = 0;
}

This is the HTML code in the Parent component:

<h1>{{title}}</h1>
<p>Count: {{currentCount}}</p>
<app-plus [count]="currentCount" ></app-plus>

This is the TypeScript file in the Child Increment component:

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

@Component({
  selector: 'app-plus',
  templateUrl: './plus.component.html',
  styleUrls: ['./plus.component.css']
})
export class PlusComponent implements OnInit {
  @Input() count:any;
  @Output() countUpdatePlus = new EventEmitter<string>();

  constructor() { }

  ngOnInit(): void {
  }

  onPlus() {
    this.count ++
  }
}

This is the HTML code in the Child Increment component:

<button (click)="onPlus()">++</button>
<h1>Here is {{count}}</h1>

Answer №1

Before proceeding, it is crucial to make some adjustments in your child component. In Angular, which utilizes Typescript, I highly recommend explicitly defining your properties:

 @Input() count: number; // rather than using count: any
 @Output() countUpdatePlus = new EventEmitter<number>(); // instead of <string>

Avoid resorting to the use of any, as it defeats the purpose of incorporating Typescript. Overusing any will lead you back to just plain javascript.

To delve deeper into this concept, refer to this resource TypeScript: Stop Using 'any', There's a Type For That

Given that you have your countUpdatePlus event emitter, ensure you implement this logic within your onPlus() function:

onPlus() {
 this.count++;
 this.countUpdatePlus.emit(this.count); // triggering the emission of your updated count property
}

Subsequently, within your parent component, be sure to capture the emitted value:

<h1>{{title}}</h1>
<p>Count: {{currentCount}}</p>
<app-plus 
  [count]="currentCount" 
  (countUpdatePlus)="onUpdatedCounter($event)">
</app-plus>

In the parent TypeScript file:

...
onUpdatedCounter(value: number): void {
  // incorporate necessary actions with your updated counter 
}

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