The issue of data not appearing in Angular Ionic has been identified, and this problem arises due

I'm currently facing an issue with displaying data from my SQL database on a server. Even though the data is being retrieved correctly, it's not showing up in my application. Strangely, when I console.log it, everything displays perfectly in the console.

Here is the interface in TypeScript:

export interface IProduct {
  productID: string;
  productImage: string;
  productName: string;
  productDescription: string;
  productRating: number;
  productPrice: number;
}

This is the page.ts file:

export class ViewProductPage implements OnInit {

  product: IProduct;

  constructor(private service: CustomerService) { }

  ngOnInit() {
    this.service.getProduct().subscribe((data: any) => {
      this.product = data;
      console.log(this.product);
    });
  }
}

And here is the HTML code:

<ion-content color="dark">
  <div class="product-image-container">
    <div class="product-image-wrapper">
      <img [src]="'https://via.placeholder.com/1000'">
    </div>
    <div class="product-name">
      <h1>{{ product.productName }}</h1>
    </div>
  </div>
  <div class="product-description">
    <h6>Price:</h6>
    <p>{{ product.productPrice }}</p>
    <h6>Description:</h6>
    <p>{{ product.productDescription }}</p>
  </div>
</ion-content>

The error message displayed in the console is:

ERROR TypeError: can't access property "productName", ctx.product is undefined

Here is the method for getting the product:

getProduct(): Observable<IProduct> {
  return this.http.get<IProduct>(this.baseURI + 'CustomerOrder/GetProduct/' + this.productID);
}

Answer №1

When product is not initialized and there is a delay in receiving the response, then your product will remain undefined.

Only after the response is received will your product be assigned a value.

Solution 1: Utilize Optional Chaining

According to Optional chaining,

The ?. operator acts like the . chaining operator, however, it short-circuits with a return value of undefined instead of causing an error if a reference is nullish (null or undefined). It returns undefined when used with function calls if the given function does not exist.

<ion-content color="dark">
  <div class="product-image-container">
    <div class="product-image-wrapper">
      <img [src]="'https://via.placeholder.com/1000'">
    </div>
    <div class="product-name">
      <h1>{{ product?.productName }}</h1>
    </div>
  </div>
  <div class="product-description">
    <h6>Price:</h6>
    <p>{{ product?.productPrice }}</p>
    <h6>Description:</h6>
    <p>{{ product?.productDescription }}</p>
  </div>
</ion-content>

View Sample Solution 1 on StackBlitz


Solution 2: Use *ngIf to Check for product

Add *ngIf to verify product's existence and prevent accessing its inner properties when product is null or undefined.

<ion-content color="dark">
  <ng-container *ngIf="product">
    <div class="product-image-container">
      <div class="product-image-wrapper">
        <img [src]="'https://via.placeholder.com/1000'">
      </div>
      <div class="product-name">
        <h1>{{ product.productName }}</h1>
      </div>
    </div>
    <div class="product-description">
      <h6>Price:</h6>
      <p>{{ product.productPrice }}</p>
      <h6>Description:</h6>
      <p>{{ product.productDescription }}</p>
    </div>
  </ng-container>
</ion-content>

View Sample Solution 2 on StackBlitz

Please note that both solutions introduced a 5-second delay to reproduce the issue related to Observable delays.

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