Child/Nested Components in Angular: An Overview
Angular, one of the most popular front-end web development frameworks, consists of a robust architecture offering many features to build complex, scalable, and maintainable applications. One of the cornerstones of Angular’s architecture is its component-based approach, in which components are reusable, modular, and independent building blocks of an application.
A component in Angular encapsulates its own HTML template, styles, and logic. However, as an application grows more complex, a component might need to organize its internal structure into smaller pieces, involving the idea of child/nested components. In this article, we’ll explore what child/nested components are, how to create them, and some FAQs.
What are Child/Nested Components?
Child/Nested components are components that are embedded within other parent components and share a hierarchical relationship based on their functionality and structure. Nested components allow developers to break down a large component into smaller pieces, forming a tree-like structure of components that communicates with each other through inputs and outputs.
In Angular, a child/nested component resides within the template of its parent component. By using Angular’s component selectors, we can define which component to use and where it should be injected into its parent component’s DOM.
Creating Child/Nested Components
To create a child/nested component in Angular, we need to follow a few simple steps:
Step 1: Create a new component.
We can create a new component in Angular CLI using the following command:
“`
ng generate component child-component
“`
This will generate a new child component along with its CSS and HTML files.
Step 2: Define the component selector in the parent component.
In the parent component, we should add a placeholder for the child component using its selector in the parent template. For example:
“`
“`
Step 3: Implement the input/output binding.
To enable communication between the parent and child component, we define the input and output bindings. For example, the parent can pass data to the child using an input, while the child might emit events defined in an output to notify the parent component. Here is an example of how to define the input and output bindings:
“`
// parent.component.ts
import { Component } from ‘@angular/core’;
@Component({
selector: ‘app-parent’,
template: `
Parent Component
`,
})
export class ParentComponent {
parentData = “Hello from parent component”;
onChildOutput(event: any) {
console.log(‘Received output from child component:’, event);
}
}
“`
“`
// child.component.ts
import { Component, Input, Output, EventEmitter } from ‘@angular/core’;
@Component({
selector: ‘app-child’,
template: `
Child Component
Input from Parent: {{ childInput }}
`,
})
export class ChildComponent {
@Input() childInput: string = ”;
@Output() childOutput = new EventEmitter
notifyParent() {
this.childOutput.emit(‘Hello from child component’);
}
}
“`
FAQs
Q1. Why are child/nested components necessary in Angular?
A1. Child/nested components help developers to break down a large component into smaller, easier to manage pieces, resulting in better code quality and maintainability of the application.
Q2. Can a child component have its own child components?
A2. Yes, a child component can have its child components, and this structure can continue to form a tree-like structure of components.
Q3. How do you pass data from a child component to a parent component?
A3. Angular provides an output emitter, which can be used to emit events to the parent component. The parent component should listen to these events and update its state accordingly.
Q4. How do you pass data from a parent component to a child component?
A4. Angular provides an input decorator, which can be used to pass data to the child component. The parent component should set the value of the input property of the child component.
Conclusion
Child/nested components in Angular provide a structured and hierarchical way of building complex applications, making it easier to manage and maintain the application codebase. By implementing input and output bindings, the communication between these components has become more effortless, enabling the creation of reusable components that can be used across different parts of the application.