Pass Data From Parent Component To Child Component Using @Input() In Angular 9

In this article, we will learn how to pass data from parent component to child component using @Input() in Angular 9.

@Input() allow Angular to share data between the parent context and child directives or components. An @Input() property is writable.

Use the @Input() decorator in a child component to let Angular know that a property in that component can receive its value from its parent component. It helps to remember that the data flow is from the perspective of the child component. So an @Input() allows data to be input into the child component from the parent component.

Prerequisites:

• Basic knowledge of Angular
• Code editor like Visual Studio Code

Create a new Angular project by typing the following command in the VSCode terminal.

ng new parent-to-child

Now, open the newly created project and execute the commands given below. It will create two components parent and child.

ng g c parent
ng g c child

Open the parent.component.ts file and add the code in it.

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

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

  preText = 'Hello';
  list = [
    { id: 1, name: 'John' },
    { id: 2, name: 'Mark' },
    { id: 3, name: 'Deo' }
  ];

  constructor() { }

  ngOnInit(): void {
  }

}

Open the parent.component.html file and add the code in it.

<h1>{{list.length}} Names:</h1>
<app-child *ngFor="let result of list" [data]="result" [preText]="preText">
</app-child>

Open the child.component.ts file and add the code in it.

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

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

  @Input() data: any;
  @Input('preText') pre: string;

  constructor() { }

  ngOnInit(): void {
  }

}

Open the child.component.html file and add the code in it.

<h3>{{pre}}, {{data.name}}</h3>

Open the app-routing.module.ts file and add the code in it.

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { ParentComponent } from './parent/parent.component';
import { ChildComponent } from './child/child.component';

const routes: Routes = [
  {
    path: 'parent',
    component: ParentComponent,
  },
  {
    path: 'child',
    component: ChildComponent,
  }
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

Open the app.component.html file and add the code in it.

<router-outlet></router-outlet>

Output:

 

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Also, check Dynamic Page Title Based On Route In Angular 9