Angular 8 Tutorial

Angular 8 Introduction History and versions of Angular 8 Architecture of Angular 8 How to install Angular 8 and set-up it. Creating our first Angular 8 app Angular 8 app loading

Difference between Angular And react

Angular vs react

Angular 8 Advantages Disadvantage

Advantage and Disadvantage of Angular 8

Angular 8 file structure

Angular 8 file structure

Angular 8 components

Components of Angular 8

Angular 8 CLI Commands

All CLI commands of Angular

Angular 8 with Bootstrap

How to install bootstrap for Angular 8 Libraries of Angular 8

Angular 8 Routing

Routing in Angular 8

Angular 8 directives

Angular 8 Directives Angular 8 ngIf directive Angular 8 ngFor directive Angular 8 ngSwitch directive Angular 8 ngClass directive Angular 8 ngStyle directive

Angular 8 pipes

Angular 8 Pipes

Angular 8 databinding

Angular 8 Data binding Angular 8 Event binding Angular 8 Property binding Two-way data binding in Angular 8

String Interpolation In Angular 8

Angular 8 String interpolation

Angular 8 forms

Angular 8 Forms Data flow of forms in Angular 8 Creating forms in Angular 8 Testing and validation of forms in Angular 8

Error fixing in Angular 8

Error fixing in Angular 8

Dependency injection and services in Angular 8

Dependency injection services in Angular 8

Angular 8 Animations

Angular 8 Animations

Dynamic components in Angular 8

Dynamic components in Angular 8

Angular 8 Module

Angular 8 Module Deploying an angular 8 app

Introduction of unit testing in angular 8

Unit testing in angular 8

Observables in angular 8

Observables in angular 8

Angular 8 universal

Angular 8 universal

Angular 8 Changes and new features

New features and changes in Angular 8

Conclusion

Angular 8 Conclusion

Angular 8 Directives

Angular 8 Directives: Directives are instructions in the DOM (Document Object Model). It specifies how to place our business logic in Angular. The directive is markers on a DOM element that tell Angular to attach a specified behavior to that DOM element or even transform the DOM element and its children. Mostly directives in Angular starts with ng- where ng stands for Angular, and it extends the HTML.

Angular 8 Directives

There are three kinds of directives:

1. Component Directives

2. Structural Directives

3. Attribute Directives

Types of Angular 8 Directives

Component Directives

Components are the most common of the directives. It contains the details of how the component should be processed, instantiated, and used at runtime. The component comprises meta-data.

Structural Directives

Structural Directivesaredone in the elements section. These directives are used to manipulate and change the structure of the DOM elements. Structural directives have a star (*) sign before the directive. Like as,* ngIf, *ngFor, and *ngSwitch directive.

  • *ngIf Directive: The *ngIf allows us to Add/Remove DOM Element.
  • *ngSwitch Directive: The *ngSwitch will enable us to Add/Remove DOM element. It is same as the switch statement of C#.
  • *ngFor Directive: The *ngFor directive is used to repeat a part of HTML template once per each item from an iterable list (Collection).

Attributes Directives

Itdeals with changing the look and behavior of the DOM element. For example: ngClass, ngStyle etc.

  •  NgClass Directive: The ngClass Directive is used to add or remove CSS classes to an element.
  • NgStyle Directive: The ngStyle Directive facilitates you to modify the style of an HTML element using the expression. We can also use the ngStyle Directive to change the style of our HTML element dynamically.
Attributes Directives

Difference between Structural Directive and Attribute Directive

Structural Directive Attribute Directive
Structural directives are applied to <template> elements and used to add or remove content (stamp and template). The component has their view (HTML and styles) because of that, there can be one component on a host element, but multiple directives.

How to Create Custom Directives?

We can create our custom directives to use in Angular components with the help of the command line. The command which is used to develop the Directive using the command line is as follows-

ng g directive name of the Directive
e.g
ng g directive change text 

It is seen in the command line as given in the below code-

C:\projectA7\angular7-app>ng g directive change text
CREATE src/app/change-text.directive.spec.ts (241 bytes)
CREATE src /app/change-text.directive.ts (149 bytes)
UPDATE src/app/app.module.ts (565 bytes) 

The above files, i.e., change-text directive.spec.ts and change-text.directive.ts created and the app.module.ts is updated.

app.module.ts

import { BrowserModule } from ‘@angular/platform-browser’;

import { NgModule } from ‘@angular/core’;
import { AppRoutingModule } from ‘./app-routing.module’;
import { AppComponent } from ‘./app.component’;
import { NewcmpComponent } from ‘. /new-cmp.component’;
import { ChangeTextDirective } from ‘. /change-text.directive’;
@NgModule({
declarations: [
AppComponent,
NewCmpComponent,
ChangeTextDirective
],
Imports: [
BrowserModule,
AppRoutingModule
],
providers: [ ],
bootstrap: [AppComponent]
}]
export class AppModule { }  

The ChangeTextDirective class has been included in the declarations in the above file. The class is also imported from the file given below-

Change-text.directive

 Import {Directive}  from ‘@angular/core’;
@Directive ({
Selector; ‘[changeText]’
})
Export class ChangeTextDirective {
Constructor ( ) { }
} 

The above file has a directive and it also has a selector property. Whatever we define in the selector, the same has to match in the view, where we assign the custom directive.

In the app.component.html view, add the directive as follows-

 

Welcome to {{title}}.

Welcome to {{ title}}.

We will write the changes in change-text.directive.ts file as-

change-text.directive.ts

 import { Directive, elementRef} from
‘@angular/core’;
@Directive({
Selector: ‘[changeText]’’
})
Export class ChangeTextDirective {
Constructor(Element: ElementRef) {
Console.log(Element);
Element.nativeElement.innerText= “Text is changed by changeText Directive.”;
}
} 

In the above file, there is a class known as ChangeTextDirective, and also a constructor.



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