Angular-2021.md

Angular-with-TypeScript-Workshop

Setup

• Open Style Guide
• If you are using VS Code then make sure the following settings are put in place

"editor.formatOnSave": true,
"editor.insertSpaces": true,

Optionally

"files.autoSave": "onFocusChange"

Also, if you have not, install the following extensions

• Angular Language Service
• Angular Snippets
• EditorConfig for VS Code

Introduction - @Discussion

• Bootstrapping your app

  • Angular CLI

• Preferred editor

  • Visual Studio Code
  • Sublime Text

• Finally,

  • What do we have?
  • what are we going to do?

Components - @Discussion

• What is a component?
• How does Angular use components?
• Hierarchy of components
• Send data down, emit events up
• No scopes, no two-way binding, no more MVC

Components - @Exercise

• Update app.component.html

<div class="container">
  <nav class="navbar navbar-expand-lg navbar-dark bg-dark navbar-toggleable-sm justify-content-center">
    <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target=".navbar-collapse">
      <span class="navbar-toggler-icon"></span>
    </button>
    <a href="/" class="navbar-brand d-flex w-50 mr-auto">Friends HQ</a>
    <div class="navbar-collapse collapse">
      <ul class="nav navbar-nav ml-auto w-100 justify-content-end">
        <li class="nav-item">
          <a class="nav-link" href="#">Dashboard</a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="#">People</a>
        </li>
      </ul>
    </div>
  </nav>
</div>
<div class="container">
  <!-- Insert your code here -->
</div>
<footer class="footer text-center">
  <nav class="navbar fixed-bottom navbar-light bg-faded">
    <a class="navbar-brand" href="#">Created by Looselytyped</a>
  </nav>
</footer>

Components - @Exercise

• See how app.component.ts is being used in app.module.ts
• Introduce variables in app.component.ts and use them in the template

Components - @Discussion

• Component hierarchy
  • Just as index.html uses app-root we can create another component, say app-child-component and use it in app.component.html
  • What does it take to create a new component?
    • Create the necessary files in the right location (Refer to Style Guide)
    • Create an index.ts file and export the component
    • declare the component in app.module.ts
    • Use it somewhere in the DOM

Components - @Exercise

• Create PeopleComponent

  • The people directory should be under src/app/
  • The selector needs to be app-people
  • The templateUrl should be people.component.html

• Update app/people/people.component.html

<div>
  <h1>People Component</h1>
</div>

• Be sure to update app.module.ts!!
• Update app.component.html and use the selector where it says <!-- Insert your code here -->

Components - @Discussion

• Now we need to display a "list" of people
• While it seems that PeopleComponent is an "empty" component, it is usual for "feature root" components to be just like the "root" component - they act as the place where you hang all the features off of

Components - @Exercise

• Create a PersonListComponent under people/person-list directory

  • Use the snippets functionality in VS code if you have it installed
  • The snippet is Ctrl-space followed by a-component then "tab" key
  • The selector should be app-person-list
  • Note that here we are using the person-list.component.css file, so be sure to introduce a styleUrls array in your @Component descriptors

• Update person-list.component.html

<div class="person-list">
  <div class="row">
    <div class="col-xs-12 col-md-9">
      <div class="list-group">
        <a href="#" class="list-group-item list-group-item-action flex-column align-items-start">
          <div class="d-flex w-100 justify-content-between">
            <h5 class="mb-1">
              <!--Display first friend here-->
            </h5>
          </div>
        </a>
      </div>
    </div>
    <div class="col-xs-12 col-md-3 sidebar">
      <a href="#" class="btn btn-success sidebar-cta disabled">
        Add someone
      </a>
    </div>
  </div>
</div>

• Update person-list.component.css

.person-list .list-group, .sidebar {
  margin-top: 20px;
}

.person-list .list-group {
  border: 1px solid #eee;
  border-radius: 3px;
}

.person-list .sidebar .btn {
  padding: 15px;
  width: 100%;
}

• Be sure to update app.module.ts!
• Use the PersonListComponent in people.component.html

Modeling - @Discussion

• Models, and mapping to entities
• Using models in your components

Modeling - @Exercise

• Define a interface called Friend in shared/friend.model.ts directory to map entities in server/api/db.json
• Declare an array of friends on PersonListComponent and initialize it to an array
  • Copy the array found in server/api/db.json to person-list.component.ts and assign it to a local variable if it makes it easier
• Display the first and last name of the first friend in that array in person-list.component.html

Components - @Discussion

• Do we need another component?
  • Whats the reuse potential?
  • Is there enough state to manage?
• How do we loop over a list of items?
  • If we are looping over a child component, how do we supply it with what it needs?

Components - @Exercise

• Create a ShowPersonComponent under people/show-person

  • selector must be app-show-person
  • Make sure you have the stylesUrl attribute set in @Component

• Ensure it has an @Input() friend: Friend attribute

• Update show-person.component.html

<a href="#" class="list-group-item list-group-item-action flex-column align-items-start">
  <div class="d-flex w-100 justify-content-between">
    <h5 class="mb-1">
      {{ friend.firstName }} {{ friend.lastName }}
    </h5>
    <small>
      <div class="heart-rating">
        <span class="fa fa-heart" data-rating="1"></span>
      </div>
    </small>
  </div>
</a>

• Update show-person.component.css

.heart-rating {
  line-height:32px;
}

.heart-rating .fa-heart, .heart-rating .fa-heart-o {
  font-size: 2em;
}

.heart-rating .fa-heart {
  color: red;
}

• Use *ngFor in person-list.component.html invoking app-show-person setting the friend attribute for each friend in the friends array

Events - @Discussion

• How do we attach events to components?
  • We can use the browser events like click and invoke a method on the component
• Given that the state of the component changes how do we conditionally apply a class to the component?
  • We can use the [ngClass] directive
  • Notice that this is a "setter" just like [friend]=friend is

Events - @Exercise

• Modify show-person.component.html to attach a click handler to heart-rating
  • Introduce a method called 'like' in ShowPersonComponent that that toggles the fav flag on the friend attribute
  • Invoke it by attaching a (click) handler in the template so that you invoke like on a click
  • To avoid event propogation you can simply do something like like(); false; in the template
• Once you do that, use ngClass to flit the class of the span between fa-heart and fa-heart-o
  • You can use tertiary statements in HTML like so (friend.fav)?'fa-heart':'fa-heart-o'

Events - @Discussion

• How do we notify the parent of an event?
  • We can use the EventEmitter and wrap anything in the event that is to be propagated
• The parent can then listen for the name of that "event" and attach a callback in the template

Events - @Exercise

• Introduce an Output event emitter in ShowPersonComponent that emits an event of type Friend

• When a friend is "liked" go ahead and emit the event wrapping the friend in it

• In PersonListComponent's template "listen" for that event, and attach a handler to set an attribute named displayBanner to true

  • NOTE that you HAVE to declare the attribute first (initialize to false) and then set it to true on receiving an event
  • Make sure that you switch displayBanner to false eventually (You can use setTimeout for this

• Here is the HTML you will need to add to person-list.component.html

<div class="col-xs-12 col-md-9">
  <div *ngIf="displayBanner" class="alert alert-success box-msg" role="alert">
    <strong>List Saved!</strong> Your changes has been saved.
  </div>
</div>

• Here is what displayBanner should look like in PersonListComponent

showBanner(friend: Friend) {
  this.displayBanner = true;
    setTimeout(() => {
      this.displayBanner = false;
    }, 3000);
  };

Services - @Discussion

• How do services work in Angular?

  • If they too have dependencies (for e.g. a service might need HttpClient) then you need to mark the service as @Injectable
  • They need to be "provided"
  • Once provided they can be injected into other components

• AJAX Calls

  • Will need HttpClient injected
  • HttpClient has methods (like get and put) return Observable-s

Services - @Exercise

DO THIS FIRST!!

• Open a new terminal and run npm run server (So now you have two terminals, one running ng serve and now this)

Then

• Import HttpClientModule from @angular/common/http in our module

• Create a FriendsService under app/shared (Use the command line ng g service shared/Friends --dry-run true and see what it does

  • Make sure it is @Injectable !!

• Inject HttpClient in it's constructor

• You will need a BUNCH of imports

import {
  HttpClient,
  HttpHeaders,
} from '@angular/common/http';
import {
  Observable,
} from 'rxjs';

• Implement a getFriends method that gets http://localhost:3000/friends and returns Observable<Array<Friend>>

  getFriends(): Observable<Friend[]> {
    return this.http.get<Friend[]>('http://localhost:3000/friends');
  }

Dependency Injection - @Discussion

• Now that we have a service, how do we use it in our components?
  • This is the same as how we used HttpClient in our FriendService!
• We also need to discuss the lifecycle of components, especially what OnInit offers us, and why it is useful

Dependency Injection - @Exercise

• Inject the FriendService in PersonListComponent
• Instead of hard-coding the array of friends, use onInit to populate the friends array like so

this.friendService.getFriends()
      .subscribe(friends => this.friends = friends);

Dependency Injection - @Discussion

• Much like HttpClient.get we also have HttpClient.put but the signature is a tad more elaborate.
  • Specifically in our situation, our backend which is the json-server that expects us to supply the right HttpHeaders else it won't do anything
  • put also requires a payload

Dependency Injection - @Exercise

• Implement saveFriend which takes a Friend as an argument, does a put on the backend with the supplied Friend as a payload, and with the right HttpHeaders. Here is what the headers look like

const headers: HttpHeaders = new HttpHeaders({
  'Content-Type': 'application/json',
  'Accept': 'application/json',
});

• Note that the backend sends you back the updated friend record!
• Go ahead and use that method in PersonListComponent's like method to save when you like/unlike a friend
  • First, inject the service in the constructor
  • Then update the like method to use saveFriend

Components - @Discussion

• Smart vs. dumb components
  • Smart components
    • Usually leverage services
    • Know how to get/load/update data
  • Dumb components
    • Fully defined via their API
    • Everything is an @Input or an @Ouput

But! Where do we save our friend? - In the PersonListComponent of course!

• Instead, when the parent PersonListComponent receives the notifyParent (which in turn invokes showBanner) it will now need to "save" the fact that a friend was "liked". Modify showBanner to first save the friend, and then showBanner

Routing - @Discussion

• How does routing work in Angular?
  • I like to use a separate file called app.routes.ts
  • This declares a Routes object which is essentially an array of Route objects
  • Each Route object introduces a path and a component to use for that path
  • We need to then install the routes as part of our imports in app.module.ts
  • Finally we need to use router-outlet in the DOM to signify which portions of the DOM get managed by the router

Routing - @Exercise

• First you need to import RouterModule into your AppModule
• Create a new file called app.routes.ts next to app.module.ts file so that we
  1. route people to use the PeopleComponent
  2. trap ** to redirectTo people
  3. Be sure to import Routes coz you will need it
• Import that file into app.module.ts and import the routes using Router.forRoot
• Update app.component.html to use router-outlet

Routing - @Discussion

• Usage of routerLink and routerLinkActive directives in the DOM

Routing - @Exercise

• Update the navbar links in app.component.html to use these two directives.
  • Remember that I have already supplied an active class to highlight which link is active

Routing - @Exercise

• Use the angular-cli to generate a DashboardComponent
  • In your terminal you will need to do ng generate component <component-name>
• Update dashboard.component.html to look like this

<div class="container">
  <div class="dashboard">
    <div class="dashboard-box dashboard-stat">
      <h2>Statistics about your account</h2>
      <ul class="list-inline">
        <li class="list-inline-item">
          <span class="stat-number">1</span>
          <span class="stat-description">Contacts</span>
        </li>
        <li class="list-inline-item">
          <span class="stat-number">2</span>
          <span class="stat-description">Kids</span>
        </li>
      </ul>
    </div>
  </div>
</div>

• Update dashboard.component.css to look like this

.dashboard {
  background-color: #fff;
  padding-top: 50px;
}

.dashboard .dashboard-box.dashboard-stat {
  margin-bottom: 40px;
  text-align: center;
}

.dashboard .dashboard-box {
  background-color: #fff;
  border: 1px solid #dfdfdf;
  border-radius: 3px;
  padding: 15px;
}

.dashboard .dashboard-box h2 {
  border-bottom: 1px solid #eee;
  font-size: 14px;
  font-weight: 600;
  padding-bottom: 5px;
}

.dashboard .dashboard-box.dashboard-stat li:not(:last-child) {
  margin-right: 25px;
}

.dashboard .dashboard-box.dashboard-stat li {
  display: inline-block;
}

.dashboard .dashboard-box.dashboard-stat .stat-number {
  display: block;
  font-size: 25px;
}

.dashboard .dashboard-box.dashboard-stat .stat-description {
  font-size: 13px;
}

• Introduce a new route that uses the DashboardComponent when the route is /dashboard
• Update the Dashboard link in app.component.html so that it links correctly and displays the right class (active) when clicked

Pipes - @Discussion

• What are pipes?
• Think of Unix pipes
• They are only meant for view transformation!!!

Pipes - @Exercise

• Use the angular cli to create a new pipe called FullName under app/people/shared
• The first argument to the transform method should be of type Friend
• The return value should be the Friend-s firstName and lastName concatenated - Use template strings here
• Use the pipe in show-person.component.html
• Can you think of how you could pass in a delimiter, like , as an argument? How will the pipe use that?

Nested Routes - @Discussion

• How does one add a /people/add route?
• How does one define a nested route?

Nested Routes - @Exercise

• First, create a PersonFormComponent under app/people/

• Modify the app.routes.ts to have two routes under people — '' that uses PeopleComponent, and add that uses PersonFormComponent

• Add the necessary router-outlet in people.component.html

• Update person-form.component.html

<div class="col-xs-12 col-md-12">
  <h1>Add a new person</h1>
</div>

• Update person-form.component.css

.ng-valid[required], .ng-valid.required  {
  border-left: 5px solid #42A948; /* green */
}

.ng-invalid:not(form)  {
  border-left: 5px solid #a94442; /* red */
}

Template forms - @Discussion

• Familiar / Simple use cases / Harder to test
• For our project
  • Is our model sufficient?
  • Maybe we should make an enum for Gender

Template forms - @Exercise

Part I

• Introduce a enum Gender under shared directory using the angular cli

  • This should have three values, one for Male, like so — Male = "male", and similarly for Female, and Undisclosed
  • Use this enum in Friend

• Create a new pipe using the cli called EnumToArrayPipe under shared

Update enum-to-array.pipe.ts to look like so

@Pipe({
  name: 'enumToArray'
})
export class EnumToArrayPipe implements PipeTransform {
  transform(data) {
    const keys = [];
    for (const enumMember in data) {
      keys.push({
        key: enumMember,
        value: data[enumMember]
      });
    }
    return keys;
  }
}

Part II

• Import FormsModule in app.module.ts
• Create a instance variable (the name of the varible should be model) of type Friend in PersonFormComponent with appropriate values
• Update person-form.component.html to look like so

<form #addNewPersonForm="ngForm"
      (ngSubmit)="onSubmit()">
  <div class="form-group">
    <label for="first-name">First name</label>
    <input type="text"
           class="form-control"
           id="first-name"
           [(ngModel)]="model.firstName"
           name="firstName"
           #firstName="ngModel"
           required>
    <div [hidden]="firstName.valid || firstName.pristine"
         class="alert alert-danger">
      First name is required
    </div>
  </div>
  <button [disabled]="!addNewPersonForm.valid"
          type="submit"
          class="btn btn-success">Submit</button>
</form>
<p>Form value: {{ addNewPersonForm.value | json }}</p>
<p>Model value: {{ model | json }}</p>

Template forms - @Discussion

• What is #addNewPersonForm="ngForm" ?
• What is [(ngModel)]="model.firstName"?
• What is name="firstName" & #firstName="ngModel"?

Template forms - @Exercise

• Fill in the form to accomodate for lastName, and fav (Note — this is a checkbox input)
• Use a select and option with the enumToArray pipe to correctly display and update the model.gender

Reactive forms - @Discussion

• Leverages programmatic API / Easier to test / Simplifies templates

Reactive forms - @Exercise

Part I

• Add FormsModule with ReactiveFormsModule in app.module.ts
• Modify person-form.component.ts to have a addNewPersonForm of type FormGroup like so

addNewPersonForm = new FormGroup({
  firstName: new FormControl(this.model.firstName),
  // ...
});

• Add the fields for other attributes in your model
• Clean up the template to use the FormGroup like so

<form [formGroup]=addNewPersonForm>
  <div class="form-group">
    <label for="first-name">First name</label>
    <input type="text"
           formControlName="firstName">
  </div>
  <button type="submit"
          class="btn btn-success">Submit</button>
</form>
<p>Form value: {{ addNewPersonForm.value | json }}</p>
<p>Model value: {{ model | json }}</p>

• Make sure you add the other fields

Reactive forms - @Discussion

• Why do we need the FormBuilder ?
  • Reduces verbosity
  • Allows for symmetry between the domain and the form
  • Particularly useful if you have a nested domain

Part II

• Inject FormBuilder into the constructor for PersonFormComponent
• Use FormBuilder.group to create the form

@Exercise

• Add addFriend method to FriendService that takes a Friend and POST-s it
  • Remember, you need the HttpHeaders here!!
• Inject FriendService into the PersonFormComponent
  • onSubmit invoke the addFriend method to save a friend to the backend

Unit testing - @Discussion

• What kinds of testing is available?
  • Unit
  • Integration
  • e2e
• What is the setup in Angular for testing?

Unit testing (Services) - @Exercise

• Update friends.service.spec.ts to look like

import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { TestBed } from '@angular/core/testing';
import { Friend, Gender } from '.';
import { BASE_URL, FriendsService } from './friends.service';

fdescribe('FriendsService', () => {
  let httpClient: HttpClient;
  let httpTestingController: HttpTestingController;
  let friendsService: FriendsService;
  let friend;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        HttpClientTestingModule,
      ],
      providers: [
      ],
    });

    httpClient = TestBed.get(HttpClient);
    httpTestingController = TestBed.get(HttpTestingController);
    friendsService = TestBed.get(FriendsService);

    friend = {
      'id': 1,
      'firstName': 'Michelle',
      'lastName': 'Mulroy',
      'gender': Gender.Female,
      'fav': true
    };
  });

  afterEach(() => {
    // After every test, assert that there are no more pending requests.
    httpTestingController.verify();
  });

  describe('#construction', () => {
    it('should be created', () => {
      expect(friendsService).toBeDefined();
    });
  });

  describe('#getFriends', () => {
    it('should get all friends', () => {
      const expectedFriends: Friend[] = [friend];

      friendsService.getFriends()
        .subscribe(data => {
          expect(data).toEqual(expectedFriends);
        });

      const req = httpTestingController.expectOne(`${BASE_URL}/friends`);

      expect(req.request.method).toEqual('GET');
      req.flush(expectedFriends);
    });
  });
});

• Following this model add a unit test to test saveFriend and addFriend

Unit testing (Controllers) - @Exercise

• Update show-person.component.spec.ts to be

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { ShowPersonComponent } from './show-person.component';
import { FullNamePipe } from '..';
import { DebugElement } from '@angular/core';
import { By } from '@angular/platform-browser';
import { Friend, Gender } from '../../shared';

fdescribe('ShowPersonComponent', () => {
  let component: ShowPersonComponent;
  let fixture: ComponentFixture<ShowPersonComponent>;
  let nameDisplayEl: DebugElement;
  let favEl: DebugElement;
  let friend: Friend;

  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [
        ShowPersonComponent,
        FullNamePipe,
      ]
    });

    friend = {
      'id': 1,
      'firstName': 'Michelle',
      'lastName': 'Mulroy',
      'gender': Gender.Female,
      'fav': true
    };

    fixture = TestBed.createComponent(ShowPersonComponent);
    component = fixture.componentInstance;

    nameDisplayEl = fixture.debugElement.query(By.css("h5.mb-1"));
    favEl = fixture.debugElement.query(By.css("span.fa"));
  });

  it('should be created', () => {
    expect(component).toBeDefined();
  });
});

• We will write the tests for this together

What's next

• Organizing
  • Use index.ts files
• Angular Forms/Router/DI
  • Routing example
• Augury
• Peformance Tips
  • Use pipes (with primitives) more than functions on components
  • Think about Lazy loading