What is the purpose of directives in Angular 2?

I am struggling to grasp the distinction between these two @Directive and directives: [HeroAppMainComponent] In the scenario presented below

 @Component({
      selector: 'hero-app',
      template: `
        <h1>Tour of Heroes</h1>
        <hero-app-main [hero]=hero></hero-app-main>`,
      styles: ['h1 { font-weight: normal; }'],
      directives: [HeroAppMainComponent]
    })

and..

import { Directive, ElementRef, Input } from '@angular/core';
@Directive({ selector: '[myHighlight]' })
export class HighlightDirective {
    constructor(el: ElementRef) {
       el.nativeElement.style.backgroundColor = 'yellow';
    }
}

Answer №1

In simple terms, directives do not come with a template, unlike components. Different types of directives include:

Answer №2

In Angular 2, directives are still a crucial part of the framework. While components are considered the primary type of directive, they are not the only option available. Components essentially represent directives that include a template, but it is still possible to create decorator-style directives without templates. Unlike Angular 1, Angular 2 does not have a .directive function. Instead, directives are implemented using simple classes that are annotated to define their behavior. To import a Component in Angular 2, the following annotation is used:

import {Component} from 'angular2/core';

Answer №3

Hey there, I hope everything is going well for you.

After reviewing the code snippets you provided, it seems like you might be struggling with understanding the difference between two terms in Angular. Let me break it down for you step by step.

The first code snippet you shared looks like this:

 @Component({
  selector: 'hero-app',
  template: `
    <h1>Tour of Heroes</h1>
    <hero-app-main [hero]=hero></hero-app-main>`,
  styles: ['h1 { font-weight: normal; }'],
  directives: [HeroAppMainComponent]
})

This snippet represents a Component, as indicated by the '@Component' selector. Components are essential building blocks in Angular that allow you to combine HTML code (typically found in a TypeScript file) with logic, like this:

app.component.html

<a [href] = "link">Link to...</a>

app.component.ts

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

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit, OnDestroy {
  link : any = 'https: www.google.com';

  constructor(){

  }

  ngOnInit() : void {
    
  }

  ngOnDestroy(): void {

  }
}

The second snippet you shared is related to a Directive (identified by '@Directive'). Directives focus solely on logic to manipulate DOM functionality in your application, such as modifying the structure of a dropdown menu upon interaction. With Directives, you only write logic and do not include HTML templates. Here's a basic example:

import { Directive, ElementRef } from '@angular/core';
@Directive({
    selector: '[appHighlight]'
})
export class HighlightDirective {
    constructor(private eleRef: ElementRef) {
        eleRef.nativeElement.style.background = 'red';
    }
}

In this directive example, we are changing the background color of a selected DOM element for highlighting purposes.

In summary, Components encompass both HTML (template) and TypeScript (logic), while Directives are limited to TypeScript (logic) only.

If you need more clarity on the differences between Components and Directives, you can check out this resource here. I hope this explanation helps you understand better.

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