Advanced Components and Directives in Angular: Building Complex Web Applications

In this section, we'll focus on creating more complex and advanced components and directives in Angular. You'll learn the basics of building advanced components with custom events and inputs, working with advanced directives like structural and attribute directives, and utilizing Angular's built-in structural directives to manipulate the DOM.

By the end of this section, you'll have the knowledge and skills to create more intricate and advanced components and directives in your Angular applications. Let's dive in and unlock the potential of Angular's powerful features!

Learning Outcomes:

• Understand how to create more complex and advanced components and directives in Angular.
• Learn how to work with advanced directives like structural and attribute directives in Angular.
• Use Angular's built-in structural directives to manipulate the DOM.
• Understand advanced techniques for creating reusable and scalable components and directives in Angular.

Prerequisites:

• Basic knowledge of HTML, CSS, and JavaScript is required.
• Familiarity with a text editor and command-line interface is recommended.
• Familiarity with Angular basics, such as creating a new project and running the app, is recommended.

Creating Advanced Components with Custom Events and Inputs

Angular components are the building blocks of any Angular application. They help create dynamic and reusable user interfaces. In this section, we will cover the different types of Angular components and how to create advanced components with custom events and inputs. We will also explore component lifecycle hooks and how they can be used to control component behavior.

Understanding the Different Types of Angular Components

Angular components can be divided into three main categories:

1. Presentational Components: These components are responsible for displaying the UI and do not have any direct knowledge of or interaction with services or data stores. They primarily receive data through inputs and emit events through outputs.
2. Container Components: These components are responsible for managing the application's state, services, and data stores. They pass data to presentational components through inputs and handle events from presentational components through outputs.
3. Smart Components: These components combine the features of both presentational and container components. They manage the application's state, services, and data stores while also displaying the UI.

Creating Advanced Components with Custom Events and Inputs

To create an advanced Angular component, we need to define custom inputs and outputs. Inputs are used to pass data from a parent component to a child component, and outputs are used to emit events from the child component to the parent component.

Let's create a simple presentational component called rating that displays a rating value and emits an event when the rating is changed:

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

@Component({
  selector: 'app-rating',
  template: `
    <div>
      <span *ngFor="let star of stars" (click)="onStarClick(star)">
        {{ star <= rating ? '★' : '☆' }}
      </span>
    </div>
  `,
})
export class RatingComponent {
  @Input() rating: number;
  @Output() ratingChanged = new EventEmitter<number>();

  stars: number[] = [1, 2, 3, 4, 5];

  onStarClick(star: number): void {
    this.rating = star;
    this.ratingChanged.emit(this.rating);
  }
}

In the above code, we use the @Input() decorator to define a rating input property and the @Output() decorator to define a ratingChanged output property. The onStarClick method is used to update the rating value and emit the ratingChanged event.

Using Component Lifecycle Hooks to Control Component Behavior

Component lifecycle hooks are special methods that Angular calls at specific points in a component's lifecycle. Some common lifecycle hooks include ngOnInit, ngOnChanges, ngDoCheck, ngAfterContentInit, ngAfterContentChecked, ngAfterViewInit, and ngAfterViewChecked.

In our rating component, we can use the ngOnInit lifecycle hook to set an initial rating value:

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

@Component({ /*...*/ })
export class RatingComponent implements OnInit {
  /*...*/

  ngOnInit(): void {
    this.rating = this.rating || 1;
  }
}

In this example, we implement the OnInit interface and add the ngOnInit method to our RatingComponent. Inside the ngOnInit method, we set the initial rating value to 1 if it hasn't been provided by the parent component.

By using custom events, inputs, and component lifecycle hooks, you can create advanced Angular components that are more flexible, dynamic, and reusable.

Working with Advanced Directives

Directives in Angular are used to manipulate the DOM and add custom behaviors to HTML elements. They can be divided into three categories: components, attribute directives, and structural directives. In this section, we will explore the different types of directives in Angular, create advanced directives with custom behaviors and properties, and work with structural and attribute directives.