An issue occurred: Unable to access the 'name' property because it is undefined

The program is not recognizing the property name. I am using the Input() function and an API to display all tweets from my API. Despite trying various solutions like changing names and properties, it still doesn't work. Is there a simple way to resolve this issue?

tweet.component.html

<mat-card>
  <mat-card-header>
    <mat-card-title>
     {{ tweet.name}}
    </mat-card-title>
    <mat-card-subtitle>added on {{ tweet.created | date: longDate }}</mat-card-subtitle>
  </mat-card-header>
</mat-card>

tweet.component.ts

import { Component, OnInit, Input } from '@angular/core';
import { Tweet } from '../tweet.model';
import { TweetDataService } from 'src/app/tweet-data.service';

@Component({
  selector: 'app-tweet',
  templateUrl: './tweet.component.html',
  styleUrls: ['./tweet.component.css']
})
export class TweetComponent implements OnInit {
  @Input() public tweet: Tweet;
  constructor() { 
  }

  ngOnInit() {
  }

}

tweet.model.ts

import { Reaction } from './reaction.model';

export class Tweet{
    constructor(
        private _name: string,
        private _reactions = new Array<Reaction>(),
        private _created = new Date()
      ) {}

      static fromJSON(json: any): Tweet {
        const rec = new Tweet(
          json.text,
          json.reactions,
          json.created
        );
        return rec;
      }
      toJSON(): any {
        return {
          name: this.name,
          reactions: this.reactions.map(re => re.toJSON()),
          created: this.created
        };
      }

      get name(): string {
        return this._name;
      }
      get created(): Date {
        return this._created;
      }
      get reactions(): Reaction[] {
        return this._reactions;
      }
      addReaction(text: string) {
        this._reactions.push(new Reaction(text));
      }


}

dataservice

import { Injectable } from '@angular/core';

import { Observable, Subject, of } from 'rxjs';
import { map, catchError, tap } from 'rxjs/operators';
import { environment } from 'src/environments/environment';
import { HttpClient } from '@angular/common/http';
import { Tweet } from './tweet/tweet.model';

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

  public loadingError$ = new Subject<string>();

  constructor(private http: HttpClient) {}

  get recipes$: Observable<Tweet[]> {
    return this.http.get(`${environment.apiUrl}/Tweet/`).pipe(
      catchError(error => {
        this.loadingError$.next(error.statusText);
        return of(null);
      }),
      map((list: any[]): Tweet[] => list.map(Tweet.fromJSON))
    );
  }

  addNewTweet(tweet: Tweet) {
    return this.http.post(`${environment.apiUrl}/tweets/`, tweet.toJSON());
  }

  getTweet$(id): Observable<Tweet> {
    console.log(`${environment.apiUrl}/tweets/${id}`);
    return this.http
      .get(`${environment.apiUrl}/tweets/${id}`)
      .pipe(map((rec: any): Tweet => Tweet.fromJSON(rec)));
  }
}

Answer №1

Often times, the issue arises due to a data synchronization problem with the service provider. A simple solution to this problem is to use the safe navigation operator (?) as shown below.

<mat-card>
  <mat-card-header>
    <mat-card-title>
     {{ tweet?.name}}
    </mat-card-title>
    <mat-card-subtitle>added on {{ tweet?.created | date: longDate }}</mat-card-subtitle>
  </mat-card-header>
</mat-card>

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