Sådan opbygges din første Ionic 4-app med API-opkald

Så du bemærkede bare, at Ionic 4 blev frigivet, og du endelig vil komme i gang med udvikling af app på tværs af platforme? Nå, i dag er din dag! Vi gennemgår opbygningen af ​​din første Ionic 4-applikation med HTTP-opkald til Open Movie Database!

Uanset om du er helt ny til Ionic eller har brugt tidligere versioner, gennemgår vi alt det grundlæggende. Vi vil dække, hvordan du opretter en ny app , routing og endda API-opkald til at vise asynkroniserede data i vores app.

Hvis du vil lære Ionic endnu hurtigere, kan du også tjekke mit Ionic Academy, som blev lavet til udviklere ligesom dig!

Klar ? !

Opsætning af vores Ionic 4-app

Hvis du er ny hos Ionic, skal du sikre dig, at du har installeret Node Package Manager. Hvis du har arbejdet med andre webteknologier, før chancerne er ret gode, har du allerede alt, hvad du har brug for.

Hvis du heller ikke har brugt Ionic før, skal du installere det via npm. Når du er installeret, er du endelig klar til at oprette dit Ionic 4-projekt!

For at oprette et tomt projekt kan du bruge Ionic CLI, så vi ender med et nyt Ionic 4-projekt med kantet support ( du kan også bruge React eller Vue, bedre support kommer senere på året ).

Når projektet er oprettet, cd vi ind i mappen. Vi bruger CLI, som bruger Angular CLI under emhætten, til at oprette nye sider til vores app, som vi vil have vist.

# Install Ionic if you haven't before npm install -g ionic # Create a blank new Ionic 4 app with Angular support ionic start movieApp blank --type=angular cd movieApp # Use the CLI to generate some pages and a service ionic g page pages/movies ionic g page pages/movieDetails ionic g service services/movie

Du kan nu direkte få din app op ved at køre følgende kommando inde i dit projekt:

ionic serve

Dette åbner browseren med preview af din app, som genindlæses automatisk, når du ændrer noget inde i dit projekt.

Når vi taler om projektet, har vi en masse filer og mapper herinde, lad os se hvad alt dette betyder. Vi vil fokusere på src- mappen i vores app, da vi ikke behøver at bekymre os om resten for nu.

App

Dette er den mappe, hvor vi foretager alle de kodeændringer, der følger senere i denne vejledning. Den indeholder allerede en hjemmemappe , der dybest set er en side, som vi oprettede før. Jeg kan godt lide at have alle sider i deres egen sidemappe , så du også kan fjerne hjemmemappen for nu.

De sider mappe indeholder de faktiske visninger / sider i vores app, hvilket betyder, at elementet vi vil se på skærmen. Lige nu har vi allerede 2 sider herinde, og hver side, du opretter med CLI, leveres med 4 filer:

  • * .module.ts: Vinkelmodulet til en side. Hver side er grundlæggende deres eget modul (relateret til den kantede arkitektur) med import og styling
  • * .page.html: HTML- markeringen for en side
  • * .page.scss: Stylingen til den specifikke side (mere om global styling senere)
  • * .page.spec.ts: En ekstra automatisk teste fil til din side. Godt, hvis du vil oprette automatiserede enhedstests
  • * .page.ts: Controlleren til en side, der indeholder Javascript-koden, der administrerer funktionaliteten

De tjenester mappe indeholder vores tidligere oprettede tjeneste - det handler om strukturering din app i henhold til bedste praksis og adskiller bekymringer mellem udsigten og de faktiske data for din app. Tjenesten tager sig af håndtering af API-opkald og returnerer blot dataene til vores syn senere!

Aktiver

Denne mappe indeholder alle de billeder, skrifttyper eller de aktiver, du har brug for til din app senere på vejen.

Miljøer

Fra tid til anden kan dit projekt have et udviklings-, iscenesættelses- og produktionsmiljø med forskellige servere, som din app er målrettet mod. Miljømappen hjælper med at opsætte oplysninger til forskellige miljøer. Vi kan senere bygge vores Ionic-app med et kommandolinjeflag, og det tager automatisk de rigtige værdier. Meget praktisk!

Tema

Denne mappe indeholder kun variablerne. Scss, der indeholder foruddefinerede farveoplysninger fra Ionic. Vi kan altid ændre denne fil og endda bruge et værktøj som Ionic Color Generator til at oprette vores egen aromatiserede version af denne fil!

Uden for mappen har vi også global.scss. Her kan vi skrive nogle SCSS, der vil blive anvendt globalt til vores app. Vi kan også definere det kun for en side i deres egne stylingfiler.

Andre filer

Den mest relevante af de andre filer kan være index.html, for ligesom med alle andre websteder markerer denne fil indgangspunktet for vores app! For nu, selvom vi ikke behøver at ændre noget herinde, så lad os nu begynde at komme ind i den faktiske kode.

Forudsat routing og HTTP-opkald

Med Ionic 4 går vi videre fra et proprietært routingskoncept til standard Angular Router. Markeringen ser måske lidt sværere ud i starten, men det giver faktisk helt mening.

For alle forbindelser inde i din app konfigurerer du routingoplysninger på forhånd - ligesom du navigerer rundt på et websted!

I vores app har vi brug for 2 ruter:

  • / film - Naviger til vores første side, der skal vise en liste over film
  • / film /: id - Vi vil være i stand til at vise detaljerne for en film, så vi tilføjer et param : id til ruten, som vi dynamisk kan løse

Vi er også nødt til at forbinde den tilsvarende side ( mere specifikt : modulet på siden) til ruten, så Angular ved, hvordan man løser en bestemt rute. Vi leverer disse oplysninger ved hjælp af loadChildren, som faktisk kun får en streng til modulstien .

Dette betyder, at vi ikke rigtig importerer et andet modul her, derfor bruger siderne doven indlæsning. Det betyder, at de kun indlæses, når vi navigerer derhen!

For at konfigurere vores routingsoplysninger skal du åbne vores app / app-routing.module.ts og ændre den til:

import { NgModule } from '@angular/core'; import { Routes, RouterModule } from '@angular/router'; const routes: Routes = [ { path: '', redirectTo: 'movies', pathMatch: 'full' }, { path: 'movies', loadChildren: './pages/movies/movies.module#MoviesPageModule' }, { path: 'movies/:id', loadChildren: './pages/movie-details/movie-details.module#MovieDetailsPageModule' } ]; @NgModule({ imports: [RouterModule.forRoot(routes)], exports: [RouterModule] }) export class AppRoutingModule { }

By making this change we have also disconnected the home page which was initially in the project (and which you might have deleted already at this point).

Now the app will load our movies page as the first page, great! You should also notice this change in your running ionic serve instance already.

Tip: If you want to get a better feeling for how your app will look on a real device you can also run ionic lab instead of serve but you have to install the package upfront:

# Install the Lab Package npm i @ionic/lab # Run your app with device preview and platform styles ionic lab

This package was previously bundled with every new app but needs to be installed for Ionic 4 now.

/Tip End

We also need to apply another change to our app as we want to make HTTP calls. Therefore we need to import another Angular module for making those requests.

The way of doing this is the same as with Ionic 3. We just need to add the HttpClientModule to our main module file and add it to the array of imports like this inside our app/app.module.ts:

import { NgModule } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { RouteReuseStrategy } from '@angular/router'; import { IonicModule, IonicRouteStrategy } from '@ionic/angular'; import { SplashScreen } from '@ionic-native/splash-screen/ngx'; import { StatusBar } from '@ionic-native/status-bar/ngx'; import { AppComponent } from './app.component'; import { AppRoutingModule } from './app-routing.module'; import { HttpClientModule } from '@angular/common/http'; @NgModule({ declarations: [AppComponent], entryComponents: [], imports: [BrowserModule, IonicModule.forRoot(), AppRoutingModule, HttpClientModule], providers: [ StatusBar, SplashScreen, { provide: RouteReuseStrategy, useClass: IonicRouteStrategy } ], bootstrap: [AppComponent] }) export class AppModule {}

Before we dive into more Ionic 4 code we first have to set up the service that powers our app and handles all the HTTP requests that we later want to call.

Making HTTP Requests

A service is the same as in previous versions a provider and can be injected into our controller in order to call its functions.

In order to use the Open Movie Database you need to request an API key and insert it into our service — the process is free so go ahead right now.

With the API we can now search for strings and get results in form of movies, episodes or even games. Also, we can get detailed information for one specific object of those results so a perfect use case for our first Ionic 4 app!

Our service only needs 2 functions:

  • searchData(): This function searches for results to a specific title and search type – an enum we defined upfront to represent the types that we can pass to the API using TypeScript!
  • getDetails(): This function returns the detailed information for one specific element, will be used on our details page

Both functions will return an Observable which is like a Promise on steroids. No serious, it’s like a stream of events that we can subscribe to. Explaining this concept would take another post. For now, let’s use it and keep in mind that both of our functions are async — they will return the API data not immediately.

Now go ahead and change your services/movie.service.ts to:

import { Injectable } from '@angular/core'; import { HttpClient } from '@angular/common/http'; import { Observable } from 'rxjs'; import { map } from 'rxjs/operators'; // Typescript custom enum for search types (optional) export enum SearchType { all = '', movie = 'movie', series = 'series', episode = 'episode' } @Injectable({ providedIn: 'root' }) export class MovieService { url = '//www.omdbapi.com/'; apiKey = ''; // <-- Enter your own key here! /** * Constructor of the Service with Dependency Injection * @param http The standard Angular HttpClient to make requests */ constructor(private http: HttpClient) { } /** * Get data from the OmdbApi * map the result to return only the results that we need * * @param {string} title Search Term * @param {SearchType} type movie, series, episode or empty * @returns Observable with the search results */ searchData(title: string, type: SearchType): Observable { return this.http.get(`${this.url}?s=${encodeURI(title)}&type=${type}&apikey=${this.apiKey}`).pipe( map(results => results['Search']) ); } /** * Get the detailed information for an ID using the "i" parameter * * @param {string} id imdbID to retrieve information * @returns Observable with detailed information */ getDetails(id) { return this.http.get(`${this.url}?i=${id}&plot=full&apikey=${this.apiKey}`); } }

I’ve also added some documentation to the functions — with a tool like Compodoc you could now create nice documentation!

Alright, now we are finally ready for some more Ionic 4 code!

Searching for Movies

We start our apps functionality with the things that happen in the background and then build the view on top of it.

So right now we need to implement the logic to submit a search term and type to our service and receive the results. Therefore, we inject the service through our constructor so it’s available to the class.

In another function that we call searchChanged() we will now simply call the according function of our service and set the result to a local variable b>results. Our view will later handle the data that comes from the API and display it using this variable.

We also keep 2 more variables for the searchTerm and type inside our class that we pass to the service. We will connect with them from the view as well so we can change them.

Now go ahead with the code for your controller inside the pages/movies/movies.page.ts:

import { MovieService, SearchType } from './../../services/movie.service'; import { Component, OnInit } from '@angular/core'; import { Observable } from 'rxjs'; @Component({ selector: 'app-movies', templateUrl: './movies.page.html', styleUrls: ['./movies.page.scss'], }) export class MoviesPage implements OnInit { results: Observable; searchTerm: string = ''; type: SearchType = SearchType.all; /** * Constructor of our first page * @param movieService The movie Service to get data */ constructor(private movieService: MovieService) { } ngOnInit() { } searchChanged() { // Call our service function which returns an Observable this.results = this.movieService.searchData(this.searchTerm, this.type); } }

Now the view which looks a lot like Ionic 3 code, just a few of the elements changed their names and properties. For everyone new to Ionic in general: Welcome to your first Ionic components!

A page can be separated into 3 areas: Header, content, footer. In our case, we don’t want a footer so we only define the header area with a title and the content with our actual elements for the search.

The first element that affects the search is the ion-searchbar which is a simple input you have seen in many apps before to search for a term.

We always want to call our search functionality when the type or searchTerm changes. We can do this by catching the (ionChange) event of some of our elements.

Below we got a select drop down with options and the according value for the different types that we could pass back to the API.

You should have also noticed the [(ngModel)] syntax through which both elements are connected to our controller properties. If one side changes, the other will automatically get the new value as well (also known as 2-way data binding).

So we got the search in place and now add another list with elements below our previous components.

For the list, we use an iteration over our results variable. Because this variable is an Observable (remember the implementation in our service) we need to add an Angular Pipe “| async” to it. The view subscribes to the Observable and handles the changes accordingly.

We also add the routing directly to this element by using [routerLink]. We construct the path that we want to open when we click on the element. We use the imdbID property of the item so we can resolve the information on our details page later.

Besides that, we create the markup for one item using the Poster which is an image, the title, year and finally also a cool icon at the and based on the type of the item. Yes, those cool icons are already bundled with your app and are called Ionicons!

With all of that in mind change your pages/movies/movies.page.html to:

  My Movie Search      Select Searchtype  All Movie Series Episode      

{{ item.Title }}

{{ item.Year }}

By now you should be able to search for a specific term inside your app and get a list of results — that’s already a big win!

If you are coming form Ionic 3 you might have also noted another new property called slot so here’s some info on that:

Ionic 4 components are built using Stencil (yeah, they actually created that tool as well!) so they are standard web components — you could import them basically everywhere on the web! These components also use the Shadow DOM API and are basically living outside of the scope of your regular DOM elements.

That means also standard styling will sometimes not affect these components like it was possible in previous versions!

In order to get information into these components, we can inject certain parts of HTML into their slots that are defined on these elements. You can see how their implementation looks like on the example of the ion-item we used here.

Presenting Detailed Information

Ok enough of background information, let’s put some more work into the details page of our app. We have implemented a route and we also created a button that passed an ID with that route so the details page will be open, but we need to get access to the ID!

With previous Ionic versions we could easily pass whole objects to new pages, this is now not a best practice anymore. Instead, we pass only small chunks of information (like an ID) with the URL. Otherwise, you would end up with a huge JSON stringified term inside the URL. This isn’t really something we want to have.

To get access to this ID field (that we already defined inside our routing in the beginning) we can use the ActivatedRoute and its properties.

So after we extract the ID from the params we can make another call to our service (that we injected through the constructor again) and get the detailed information for whatever ID we got.

Nothing really new so let’s add the following code to our pages/movie-details/movie-details.page.ts:

import { MovieService } from './../../services/movie.service'; import { Component, OnInit } from '@angular/core'; import { ActivatedRoute } from '@angular/router'; @Component({ selector: 'app-movie-details', templateUrl: './movie-details.page.html', styleUrls: ['./movie-details.page.scss'], }) export class MovieDetailsPage implements OnInit { information = null; /** * Constructor of our details page * @param activatedRoute Information about the route we are on * @param movieService The movie Service to get data */ constructor(private activatedRoute: ActivatedRoute, private movieService: MovieService) { } ngOnInit() { // Get the ID that was passed with the URL let id = this.activatedRoute.snapshot.paramMap.get('id'); // Get the information from the API this.movieService.getDetails(id).subscribe(result => { this.information = result; }); } openWebsite() { window.open(this.information.Website, '_blank'); } }

We also added another function to open a website using the window object and the information from the data of the API that we stored in the local information variable.

Now we just need to create a view based on the JSON information of the API. It always helps to log() out the info you got so you see keys that you can use to display some values.

In our case, we use the Ionic card component and add the image and some items with information and more icons (did I say I really like the Ionicons?).

We also added a button below that card that will be displayed if the result information contains the website key. We just have to add our function to the (click) event of the button in order to hook everything up!

On another note, we also have to add an ion-back-button to the header of that page in order to get a nice little back arrow to our previous movie list page. This was automatically done in v3 but needs to implemented manually as of v4!

Now finish your details view by changing your pages/movie-details/movie-details.page.html to:

     {{ information?.Genre }}       {{ information.Title }}   {{ information.Year }}     {{ information.Plot }}   {{ information.imdbRating }}    {{ information.Director }}    {{ information.Actors }}    Open Website    

If you now take a look at your browser you might notice that the image looks waaaay to big as its taking all the space available. Let’s change this through some good old CSS so open your pages/movie-details/movie-details.page.scss and insert:

.info-img { max-height: 30vh; object-fit: contain; padding: 10px; }

Now our results look a lot more appealing.

We can search, select a movie type, dive into a search result and have a fully functional Ionic 4 app with HTTP calls finished!

Conclusion

While it was a straight forward experience to build our first Ionic 4 app there are so many things we haven’t talked enough about.

UI patterns like Tabs and side menu, CSS variables, responsive layout and PWA to just name a few on the side of Ionic and Angular.

And we haven’t even touched the Cordova side of things to actually build this app into a real native mobile app!

If you want to learn how to develop Ionic 4 apps as fast as possible and get them to the iOS & Android app stores quickly you can join the Ionic Academy today and enjoy expert screencasts, a library of quick wins and a community to support you on your journey!

And of course, I (Simon) am also present inside to answer all your questions all the time

You can also find a video version of this guide below!

Oprindeligt offentliggjort på ionicacademy.com den 24. januar 2019.