Typescript: Type X is missing the following properties from type Y length, pop, push, concat, and 26 more. [2740]

Question

I have this Product interface:

export interface Product{
  code: string;
  description: string;
  type: string;
}

Service with method calling product endpoint:

  public getProducts(): Observable<Product> {
    return this.http.get<Product>(`api/products/v1/`);
  }
  

And component where I use this service to get the Products.

export class ShopComponent implements OnInit {
    public productsArray: Product[];
    
    ngOnInit() {
        this.productService.getProducts().subscribe(res => {
          this.productsArray = res;
        });
    }
}

With this state I'm getting error:

[ts] Type 'Product' is missing the following properties from type 'Product[]': length, pop, push, concat, and 26 more. [2740]

Removing typing on productsArray variable removes the error, but don't get why this is not working, since server response is an array of objects in the type of Products?

Answer 1

You are returning Observable<Product> and expecting it to be Product[] inside subscribe callback.

The Type returned from http.get() and getProducts() should be Observable<Product[]>

public getProducts(): Observable<Product[]> {
    return this.http.get<Product[]>(`api/products/v1/`);
}