Cómo construir su primera aplicación Ionic 4 con llamadas API

¿Entonces acabas de notar que se lanzó Ionic 4 y finalmente quieres comenzar con el desarrollo de aplicaciones multiplataforma? Bueno, hoy es tu día! ¡Pasaremos por la construcción de su primera aplicación Ionic 4 con llamadas HTTP a Open Movie Database!

Ya sea que sea completamente nuevo en Ionic o haya utilizado versiones anteriores, repasaremos todos los conceptos básicos. Cubriremos cómo configurar una nueva aplicación , enrutamiento e incluso llamadas a API para mostrar datos asíncronos dentro de nuestra aplicación.

Si quieres aprender Ionic aún más rápido, también puedes consultar mi Academia Ionic, que fue hecha para desarrolladores como tú.

Listo ? ¡ Vaya !

Configuración de nuestra aplicación Ionic 4

Si es nuevo en Ionic, debe asegurarse de tener instalado Node Package Manager. Si ha trabajado con otras tecnologías web antes, es muy probable que ya tenga todo lo que necesita.

Si tampoco ha usado Ionic antes, debe instalarlo a través de npm. Una vez instalado, ¡finalmente estará listo para crear su proyecto Ionic 4!

Para configurar un proyecto en blanco, puede usar la CLI de Ionic para que terminemos con un nuevo proyecto de Ionic 4 con soporte Angular ( también puede usar React o Vue, un mejor soporte vendrá más adelante este año ).

Una vez creado el proyecto, ingresamos en la carpeta. Usamos la CLI, que usa la CLI angular debajo del capó, para crear nuevas páginas para nuestra aplicación que queremos mostrar.

# 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

Ahora puede abrir directamente su aplicación ejecutando el siguiente comando dentro de su proyecto:

ionic serve

Esto abrirá el navegador con la vista previa de su aplicación que se recargará automáticamente una vez que cambie algo dentro de su proyecto.

Hablando del proyecto, tenemos un montón de archivos y carpetas aquí, veamos qué significa todo esto. Nos centraremos en la carpeta src de nuestra aplicación, ya que no tenemos que preocuparnos por el resto por ahora.

Aplicación

Esta es la carpeta donde realizaremos todos los cambios de código que siguen más adelante en este tutorial. Ya contiene una carpeta de inicio que es básicamente una página como la que creamos antes. Me gusta tener todas las páginas en su propia carpeta de páginas para que puedas eliminar la carpeta de inicio también por ahora.

La carpeta de páginas contiene las vistas / páginas reales de nuestra aplicación, lo que significa el elemento que veremos en la pantalla. En este momento ya tenemos 2 páginas aquí, y cada página que crea con la CLI viene con 4 archivos:

  • * .module.ts: El módulo angular de una página. Cada página es básicamente su propio módulo (relacionado con la arquitectura Angular) con importaciones y estilo
  • * .page.html: el marcado HTML de una página
  • * .page.scss: el estilo de la página específica (más sobre el estilo global más adelante)
  • * .page.spec.ts: un archivo de prueba agregado automáticamente para su página. Bueno si desea configurar pruebas unitarias automatizadas
  • * .page.ts: el controlador de una página que contiene el código Javascript que administra la funcionalidad

La carpeta de servicios contiene nuestro servicio creado previamente; se trata de estructurar su aplicación de acuerdo con las mejores prácticas y separar las preocupaciones entre la vista y los datos reales de su aplicación. El servicio se encargará de manejar las llamadas a la API y simplemente devolverá los datos a nuestra vista más tarde.

Bienes

Esta carpeta contiene todas las imágenes, fuentes o cualquier recurso que necesite para su aplicación más adelante.

Ambientes

De vez en cuando, su proyecto puede tener un entorno de desarrollo, preparación y producción con diferentes servidores a los que apunta su aplicación. La carpeta de entorno ayuda a configurar información para diferentes entornos. Más tarde, podemos construir nuestra aplicación Ionic con una bandera de línea de comando y automáticamente toma los valores correctos. ¡Muy útil!

Tema

Esta carpeta solo contiene el archivo variables.scss que contiene información de color predefinida de Ionic. ¡Siempre podemos cambiar este archivo e incluso usar una herramienta como Ionic Color Generator para crear nuestra propia versión con sabor de este archivo!

Fuera de la carpeta también tenemos global.scss. Aquí podemos escribir algunos SCSS que se aplicarán globalmente a nuestra aplicación. También podemos definirlo solo para una página en sus propios archivos de estilo.

Otros archivos

El más relevante de los otros archivos podría ser el index.html porque al igual que con cualquier otro sitio web, este archivo marca el punto de entrada a nuestra aplicación. Por ahora, aunque no necesitamos cambiar nada aquí, comencemos ahora a entrar en el código real.

Enrutamiento de requisitos previos y llamadas HTTP

Con Ionic 4 pasamos de un concepto de enrutamiento patentado al enrutador angular estándar. El marcado puede parecer un poco más difícil al principio, pero en realidad tiene mucho sentido.

Para todas las conexiones dentro de su aplicación, configura la información de enrutamiento por adelantado, ¡al igual que navega en un sitio web!

En nuestra aplicación necesitamos 2 rutas:

  • / películas : navega a nuestra primera página, que debería mostrar una lista de películas
  • / movies /: id : queremos poder mostrar los detalles de una película, por lo que agregamos un param : id a la ruta que podemos resolver dinámicamente

También necesitamos conectar la página correspondiente ( más específica : el módulo de la página) a la ruta para que Angular sepa resolver una ruta específica. Proporcionamos esta información utilizando loadChildren, que en realidad solo obtiene una cadena para la ruta del módulo .

Esto significa que realmente no estamos importando otro módulo aquí, por lo tanto, las páginas están usando la carga diferida. Eso significa que solo se cargarán una vez que naveguemos allí.

Para configurar nuestra información de enrutamiento, abra nuestra aplicación / app-routing.module.ts y cámbiela a:

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!

Originally published at ionicacademy.com on January 24, 2019.