第一次不加载数据

Question

I'm developing an Ionic app with angular. It has an API with php. So, I've a service that returns a JSON, the thing is, that the first time it loads the page, it doesn't load the data from the JSON.

The service:

import { Injectable } from '@angular/core';
import { HttpClient, HttpClientModule } from '@angular/common/http';

@Injectable({
providedIn: 'root'
})
export class PlayerService {

posts;

baseURL: String;

constructor(public http: HttpClient) {
    this.baseURL = 'http://127.0.0.1:8000/'
}

getPlayers() {    
this.http.get(this.baseURL + 'GetPlayers')
  .subscribe(data => {
    this.posts = data;
  });
return this.posts;
}

How I load it:

@Component({
  selector: 'app-players',
  templateUrl: './players.page.html',
  styleUrls: ['./players.page.scss'],
})
export class PlayersPage implements OnInit {

constructor(private playerService: PlayerService) { }

players = this.playerService.getPlayers();

ngOnInit() {
 }
}

HTML:

<ion-header>
  <ion-toolbar>
    <ion-buttons slot="start">
      <ion-menu-button></ion-menu-button>
    </ion-buttons>
    <ion-title>Players</ion-title>
  </ion-toolbar>
</ion-header>
<ion-content>
 <ion-list>
    <ion-item *ngFor="let p of players">
      <ion-label>
        <h2>{{p.name}}</h2>
        <h3>{{p.mail}}</h3>
      </ion-label>
    </ion-item>
  </ion-list>
</ion-content>

Answer 1

You should be returning the observable on your component, instead of the service. This will ensure the data is loaded upon initialisation of the component.

@Component({
  selector: 'app-players',
  templateUrl: './players.page.html',
  styleUrls: ['./players.page.scss'],
})
export class PlayersPage implements OnInit {

  constructor(private playerService: PlayerService) { }

  ngOnInit() {
    this.playerService.getPlayers().subscribe(data => {
      this.players = data;
    });
  }
}

And on your service.ts, make the following changes.

getPlayers() {    
  return this.http.get(this.baseURL + 'GetPlayers');
}

Do try to understand the purpose of services, and components. As stated on the Angular documentation ,

Ideally, a component's job is to enable the user experience and nothing more. A component should present properties and methods for data binding, in order to mediate between the view (rendered by the template) and the application logic (which often includes some notion of a model).

On the other hand, the duty of fetching and saving data (carrying out of HTTP requests) should be delegated to services.