Angular Workshop

[TOC]

Install VSCode

Static Design

Please find the static html pages inside design directory. Design has been done using Bootstrap 4. Original - startbootstrap.com

Get familiar with the two web pages home and manage-courses. Additionally there is form named edit-course-form which we will wrap inside a model and use to edit course details.

To watch the design in the browser,

cd design
npm install
npm start

Open http://localhost:3000/home.html or http://localhost:3000/manage-courses.html

Scaffold TheStudyMate Angular Project

Scaffold a new Angular project

Use ng new <project-name>, and follow the below selections.

$ ng new the-study-mate
? Would you like to add Angular routing? No
? Which stylesheet format would you like to use? CSS

Why Compile/Transpile?

Typescript to Javascript
JIT Compilation (Recommended during dev)
AOT Compilation (Recommended for prod)
Source Maps

Serve the project in dev mode

Use ng serve -o to serve the project in dev mode. Open files in the debugger and observe.

Observe & discuss the below

Elements tab in dev tools
Network tab in dev tools

Build & serve the project for prod mode

Use ng build --prod to build the project in the prod mode.

In order to serve using http-server follow the below steps.

npm install http-server -g
cd the-study-mate/dist/the-study-mate
http-server -o

Observe & discuss the below

dist folder
Elements tab in dev tools
Network tab in dev tools
How html templates and css files are bundled in to js files

Since Angular applications are SPAs, a simple http file server would do. Nginx and Firebase hosting are two popular ways of hosting angular apps

Configure Bootstrap CSS

Copy the html design home.html in to the app.component.html. Copy all the html code within the body tag, excluding script tags. Note that the styles aren't working.

In order to install bootstrap run npm i bootstrap. No need to install popper & jquery.

Modify angular.json to import bootstrap.min.css, as below.

projects > architect > build > styles>

"styles": [
    "node_modules/bootstrap/dist/css/bootstrap.min.css",
    "src/styles.css"
]

Angular Components

Overview

Plan the home page component hierarchy

app-root
|-nav-bar
|-carousel
|-filters
|-courses
    |-course
|-footer

Generate First Angular Component

Use ng generate component nav-bar or ng g c nav-bar to generate the nav bar component.

Note the declarations array in the NgModule decorator in app.module.ts. This how the framework will know about the existance of this component.

@NgModule({
  declarations: [
    AppComponent,
    NavBarComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Note the Component decorator in the nav-bar.component.ts

@Component({
  selector: 'app-nav-bar',
  templateUrl: './nav-bar.component.html',
  styleUrls: ['./nav-bar.component.css']
})

Move the nav-bar related html to nav-bar-component.html template file.
Add the newly created component to the DOM by adding the html custom element <app-nav-bar></app-nav-bar> to the app.component.html, using

Note: Please note that Bootstrap requires every html tag with "raw" class to follow up with a tag with "col" class. So it is a good idea to leave the layout related tags in the container component, in this case the app component.

Generate rest of the Components

Generate rest of the components as per the plan, and move the relevant html segments inside the compoenents. Then added them to the DOM using html custom elements.

Typescript jumpstart

Why we need Typescript? Well, Angular Uses Typescript by default not plain Javascript. It is not mandatory to use Typescript, but, I think, it is really hard to find documentation and examples of Angular in Javascript.

Typescript is a super set of javascript. It helps us write better code using types which javascript lacks. It mostly Javascript syntax + Types. When compiled, Typescript converts in to javascript. Go ahead with the following experiments to understand the basics of Typescript.

npm i -g typescript

Types - first.ts
Interfaces - course.ts
Classes - user.ts

Compile .ts files using tsc <filename>, and observe the generated .js files.

Note: Typescript interfaces are just types that are used during compile-time. When compiled they leave nothing in the js file. They cannot have constructor/ initialize logic. They can only have function declarations not the implementation. Lightweight and easy to use. Ideal for domain or dto objects. No encapsulation, in other words all the fields are public. Want to find out more

Note: Typescript classes are rich and heavy with initialization / constructor logic and method implementations. Want to find out more

Angular Components Diving Deeper

MV* with Angular components

Angular has a Component based architecture, and Components represent a single MVC/MVVM unit.

component.ts file in a component represents the controller/viewmodel
component.html file in a component represents the view, and uses a special html syntax

Create the model

Create a object in course.component.ts

course = {
    title: 'Angular Workshop',
    price: 50,
    description: 'Lorem ipsum dolor sit amet, consectetur adipisicing elit. Amet numquam aspernatur!',
    starRating: 4.2
  };

Bind your model to the view

Angular uses it's own html template syntax template-syntax to manipulate html.

All most every html tag is valid other than the tag
Do not use , , tags, as it doesn't make sense to repeat those onetime tags in components

Interpolation ( .ts to .html)

{{ expression }} and [targetAttribute]="expression" syntax to bind attributes from data source to view.

{{ expression }} is good to bind source attributes to html text
targetAttribute ={{ expression }} is not forbidden
[targetAttribute]="expression" is better to bind source attributes to html attributes

Event ( .html to .ts)

(event)="statement" is the syntax to bind from view target to data source

Two-way binding

Later in the forms section

Component inputs

Use @Input() decorator to define input arguments.

@Input() course;

Define a course type inline and observe the advantageous of types

@Input() course: {
    title: string;
    imgUrl: string;
    description: string;
    price: number;
    starRating?: number;
  };

Assign the input using the [targetAttribute]="expression" syntax, in the mother component courses.component.html

<app-course [course]="{
    title: 'angular workshop',
    imgUrl: 'assets/angular-logo.png',
    price: 50,
    description: 'Lorem ipsum dolor sit amet, consectetur adipisicing elit. Amet numquam aspernatur!'
  }"></app-course>

Component outputs

Use @Onput() decorator to define output argument, along with event emitter.

@Output() courseSelected = new EventEmitter<string>();

Emit the event

onClick(event: Event) {
    this.courseSelected.emit(this.course.title);
  }

Catch the event form the mother component courses.component.html

 <app-course 
    (courseSelected)="onCourseSelection($event)"
    ></app-course>

 onCourseSelection( event: string) {
     console.log( event);
   }

Angular Directives

Refactor the code

Take the inline type definition of the course to a common model course.ts
Define a courses array in the courses.ts
Import it to courses.component.ts

Types of Directives

There are three kinds of directives in Angular:

Components—directives with a template (already done)
Structural directives—change the DOM layout by adding and removing DOM elements.
Attribute directives—change the attributes or behavior of an element, component, or another directive.

Structural Directive - *ngFor

Use the courses array to generate multiple html elements

<div
    *ngFor="let course of courses"
    class="col-lg-4 col-md-6 mb-4">
    <app-course [course]="course"
    (courseSelected)="onCourseSelection($event)"
    ></app-course>
</div>

Attribute Directive - ngClass

Use ngClass to add a shadow while the course tile is within the focus.

course.component.html

<div class="card h-100"
     (click)="onClick($event)"
     (mouseenter)="mouseEnter()"
     (mouseleave)="mouseLeave()"
     [ngClass]="inFocus ? 'shadow': ''"
>

course.component.ts

  mouseEnter() {
    this.inFocus = true;
  }

  mouseLeave() {
    this.inFocus = false;
  }

Write a custom Attribute Directive - appHighlightable

Write a directive to do same, to add a shadow while the course tile is within the focus.

Generate a new directive ng generate directive highlightable highlightable.directive.ts
Receive the element ref via the constructor injection
Receive the class to add when highlighted as an input to the directive
Receive the events of the host element
Use Renderer2 the manipulate the DOM and add/remove the class
Add the directive selector, and pass the inputs to the directive

course.component.html

<div class="card h-100"
     (click)="onClick($event)"
     appHighlightable
     [appHighlightableClass]="'shadow'"
>

Angular Pipes

Use built-in pipes

Use the built-in pipe "titlecase" to format the course.title
Use the built-in pipe "currency" to format the course.price, note how the input 'EUR' is passed in

Write a custom pipes

Generate a custom pipe to implement the ellipsis behaviour

Create a custom pipe ng generate pipe ellipsis ellipsis.pipe.ts
Define the inputs and the transformation logic
Use the pipe to format course.description

Angular Routing

Refactoring

Create several page components in a new components directory
Refactor the components as below

app
|-component
  |-about
  |-contact
  |-course-details
  |-footer
  |-home
    |-courses
      |-course
    |-filter
  |-my-courses
  |-nav-bar

Move the home page body related html code from app.component.html to home.component.html

The Basics

link

Note the <base href='/'> in index.html
Imports import { RouterModule, Routes } from '@angular/router';
Define the router configs

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'my-courses', component: MyCoursesComponent },
  { path: 'contact', component: ContactComponent },
  { path: 'about', component: AboutComponent },
  { path: 'course-detail/:id', component: CourseDetailsComponent },
  { path: '', redirectTo: '/home', pathMatch: 'full' },
  { path: '**', component: PageNotFoundComponent }
];

imports: [
    BrowserModule,
    RouterModule.forRoot(routes)
  ]

Define the new page not found component
Notice the empty route
Notice the wildcard route
Notice the order of route
Add the Router Outlet placeholder replacing the app-home in the app.component.html

<app-nav-bar></app-nav-bar>

<router-outlet></router-outlet>

<app-footer></app-footer>

Router links & Activated Router links

Add router links to the nav-bar-component.html

Angular Forms

Ground work

Setup my courses component. Modify exisiting course component - course.component.html by introducing a editable mode.

Create new modal component

$ ng g c course-edit-modal

Move corresponding html the html template file. refer course-edit-modal.component.html
Add ng-bootstrap to import modal related functionality.ng-bootstrap npm install --save @ng-bootstrap/ng-bootstrap
Import the module to app.module file and add it the module imports array.

import {NgbModule} from '@ng-bootstrap/ng-bootstrap';

@NgModule({
  ...
  imports: [NgbModule, ...],
  ...
})
export class AppModule {
}

Since Angular 9 (and ng-bootstrap 6) we have to add the additional @angular/localize polyfill to our project ng add @angular/localize
Follow Modal section to implement the modal.
To summarize we need to add NgbModal service to my-courses.component.ts

constructor(private modalService: NgbModal) {}

And open the modal on create & edit events

openModal(course: Course, title: string) {
    const modalRef = this.modalService.open(CourseEditModalComponent);
    modalRef.componentInstance.title = title;
    modalRef.componentInstance.course = course;
    modalRef.result.then(
      result => console.log(result),
      reason => console.log(reason)
    );
  }

Then modify course-edit-modal.component.ts to implement the close and dismiss actions

constructor(private activeModal: NgbActiveModal) {}

  ngOnInit(): void {}

  onSave() {
    this.activeModal.close(this.course);
  }

  onClose() {
    this.activeModal.dismiss("dismissed");
  }

Add the form

First we need to add an id field to track a course identity. So we can modify a course object. refer idGenerator function

Follow the steps in Angular Reactive Forms to implement the form. refer course-edit-modal.component.ts and course-edit-modal.component.html

Follow the steps to add a validator Angular Reactive Forms Validators

Angular Component Lifecycle Hooks

Please set DEBUG = true to watch lifecycle hooks in action, in both my-courses.component.ts and course.component.ts. Here we observing the state of both input arguments and component view.

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