Encountered an error while trying to access an undefined property in Angular

Trying to perform a basic import, but encountering a significant stack trace issue.

Extensive search efforts have been made to address this problem, yet the stack trace lacks sufficient information for resolution.

UPDATE: When setting a variable not sourced from Firebase, it functions properly. The question now shifts to managing Firebase data loading upon readiness.

The pertinent files are as follows:

main.ts:

import { bootstrap }    from '@angular/platform-browser-dynamic';
import {AppComponent} from './app.component';
import { HTTP_PROVIDERS } from '@angular/http';

bootstrap(AppComponent, [HTTP_PROVIDERS]);

player.services.ts:

import { Injectable } from '@angular/core';
import {Player} from "../classes/player";

@Injectable()
export class PlayerService {

    player: Player;

    getPlayer()
    {
        return Promise.resolve(this.player);
    }

    createPlayer(uid: string, name: string, firebaseRef: Firebase)
    {
        // code omitted for brevity
    }

    setPlayer(player: Player)
    {
       // code omitted for brevity
    }
}

app.component.ts

// Code has been shortened for clarity and conciseness.
// Includes Angular components, authentication methods, and data retrieval.

export class AppComponent implements OnInit{
    
    constructor(private playerService: PlayerService) {
        // Code snippets for initializing app and user authentication
        
    }

    getPlayer() {
        // Async data retrieval function
    }

    ngOnInit() {
        this.getPlayer();
    }

     // Other methods for authenticating with various social platforms, etc.

    getName(authData: any) {
        // Extracts user name based on provider
     }
}

player-detail.component.ts

// Component to display player details

export class PlayerDetailComponent implements OnInit{
   
   @Input() player: Player;

   ngOnInit() { console.log(this.player)}
}

app.component.html

// HTML template displaying navbar, project info, and authentication buttons

player-detail.component.html

// HTML layout for player details section showing health, energy bars, and attributes

Answer №1

When providing a service, there is no need to make promises of return. A getter can be utilized instead.

private currentPlayer: Player;

get CurrentPlayer()
{
    return this.currentPlayer;
}

To implement this in your component:

    getPlayer() {

            this.firebaseData.once("value", (dataSnapshot) => {
                if (dataSnapshot.child('players').child(this.authData.uid).exists()) {
                    this.firebaseData.child('players').child(this.authData.uid).once("value", (data) => {
this.playerService.setPlayer(this.currentPlayer);                        
                        console.log(this.currentPlayer);
                    });
                } else {
                    this.playerService.createPlayer(this.authData.uid, this.getName(this.authData), this.firebaseData);
                    console.log(this.currentPlayer);
                }

            });

       ngOnInit() {
    this.currentPlayer = this.playerService.CurrentPlayer();
            this.getPlayer();
        }

If the reference is set up correctly, it will update automatically. Additionally, you can use *ngIf in the player-details component definition to display it only when the player object is not undefined.

Edit I noticed someone else mentioned using *ngIf before me, so if that resolves the issue, please refer to their solution.

Answer №2

Upon loading the PlayerDetailComponent, it was discovered that the player variable was undefined, resulting in the absence of the player object.

To address this issue, implementing the OnChanges function can solve the problem:

import { Component, Input, OnChanges, SimpleChange } from '@angular/core';
import { Player } from '../classes/player';
import {HealthBarComponent} from "./health-bar.component";
import {ChecklistComponent} from "./checklist.component";


@Component({
    selector: "player-details",
    templateUrl: "app/views/player-detail.component.html",
    styleUrls: ['app/style/player-detail.component.css'],
    directives: [HealthBarComponent, ChecklistComponent],
})

export class PlayerDetailComponent implements OnChanges{

    @Input()
    player: Player;

    ngOnChanges(changes: {[propName: string]: SimpleChange}) {
    }


}

Subsequently, including *nfIf="player" within the template ensures that the player object is not empty before rendering the element.

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