Issue with Angular filtering when utilizing pipe and mapping the response

Code snippet from shop.service.ts

getProducts(brandId?: number, typeId?: number) {
let params = new HttpParams();

if (brandId){
  params = params.append('brandId', brandId.toString());
}

if (typeId){
  params = params.append('typeId', typeId.toString());
}

return this.http.get<IPagination>(this.baseUrl + 'products', {observe: 'response', params})
  .pipe(
    map(response => {
      return response.body;
    })
  );

}

This is the code snippet from shop.component.ts:

getProducts(){
this.shopService.getProducts(this.brandIdSelected, this.typeIdSelected).subscribe(response => {
  this.products = response.data;
}, error => {
  console.log(error);
});

}

I need some guidance on why response.data is triggering an error in shop.component.ts?

Note: The error message says "Object is possibly 'null' : ts(2531)".

Answer №1

One reason for this issue is that the http.get() method may not always return a value.

this.http.get<IPagination>(this.baseUrl + 'products', {observe: 'response', params}).pipe(map(response => {
        // response.body can be null or undefined
        return response.body;
    })
);  

As a result, trying to directly access response.data without considering this possibility can lead to errors.

getProducts(){
    this.shopService.getProducts(this.brandIdSelected, this.typeIdSelected).subscribe(response => {
      this.products = response.data;
}, error => {
    console.log(error);
});

To avoid this error, it's recommended to use an if-condition before accessing the data field.

getProducts(){
    this.shopService.getProducts(this.brandIdSelected, this.typeIdSelected).subscribe(response => {
        // only assign data if response is valid
        if (response) {
            this.products = response.data;
        }

}, error => {
    console.log(error);
});

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Is there a way to adjust this validation logic so that it permits the entry of both regular characters and certain special characters?

Currently, the input field only accepts characters. If any other type of character is entered, an error will be thrown as shown in the code below. How can I update this logic to allow not only letters but also special characters like hyphens and apostrop ...

The guidelines for implementing pipes in Angular 2

I am struggling with writing a pipe that should filter for both AUID and firstname. Unfortunately, it seems to only be working for the firstname. Can anyone help me figure out why? Below is the code snippet in question: return value.filter((searc ...

Enroll in various Observers simultaneously using a loop in Angular

Currently, I am facing an issue in my code. The scenario is as follows: I need to iterate through an array of objects (orders) and perform some processing on each order. After that, I have to make multiple API calls for each product within the order' ...

Can dynamic attributes be used with ternary operators in Angular?

I attempted to alter the id of a div using Angular and implemented the following code: <div [id]="'item_' + (itemName !== undefined ? itemName.replace(' ', '-').toLowerCase() : '')"> However, when I run my te ...

Testing the NestJS service with a real database comparison

I'm looking to test my Nest service using a real database, rather than just a mock object. While I understand that most unit tests should use mocks, there are times when testing against the actual database is more appropriate. After scouring through ...

Combine and modify an object coming from a different component

Recently, I developed a customized viewer component specifically designed to showcase song sheets. One of my main objectives is to give users the ability to adjust font settings and other display preferences at their discretion. In order to accomplish this ...

Proper method for inserting a value into a string array in a React application using TypeScript

How can I properly add elements to a string array in react? I encountered an error message: Type '(string | string[])[]' is not assignable to type 'string[]' You can view the code on this playground link : Here Could it be that I&apos ...

Managing HTTP requests with errors within a forEach loop in Angular 9

I am currently coding a script that iterates through an array to make HTTP requests. Most of these requests are directed towards non-existent resources, but I do not have information on which ones specifically. Here is the code snippet I am using: ...

Implementing a Set polyfill in webpack fails to address the issues

Encountering "Can't find variable: Set" errors in older browsers during production. Assumed it's due to Typescript and Webpack leveraging es6 features aggressively. Shouldn't be a problem since I've successfully polyfilled Object.assign ...

What are the methods for handling JSON type in a web server?

Hey there! I'm currently working on making an AJAX call from the browser to a web service. The data is being sent as JSON from the browser to the web service. I'm wondering if there is a different way to retrieve it as a string and then deseriali ...

Exploring Angular 12: utilizing rxjs observables with chained subscriptions for enhanced functionality and robust error handling

Can someone help me with creating a function that I can subscribe to, returning: an observable containing the result if all operations were successful an observable with an empty string in all other scenarios foo(): void { this.uploadImage.subscr ...

Understanding TypeScript typing when passing arguments to the Object.defineProperty function

After reviewing all the suggested answers, including: in Typescript, can Object.prototype function return Sub type instance? I still couldn't find a solution, so I'm reaching out with a new question. My goal is to replicate Infix notation in J ...

Submitting an ASP.NET page should not cause the entire page to post back

My ASP.NET webpage currently has a Submit button that, upon clicking it, triggers my code to run and the page then refreshes, resulting in a full reload of the entire page. I am looking for a solution to prevent this page reload. Would implementing AJAX b ...

Transferring Viewmodel instance to a razor view within ASP .Net MVC

In my MVC Project, I have a Student model class and a Department model class. In order to establish a one-to-many relationship, I included a foreign key DepartmentID in the Student Model Class. public class Student { [Key] [DatabaseGenerated(D ...

The type 'xxxx' is not compatible with the parameter type 'JSXElementConstructor<never>'

I am currently enrolled in a TypeScript course on Udemy. If you're interested, you can check it out here. import { connect } from 'react-redux'; import { Todo, fetchTodos } from '../actions'; import { StoreState } from '../red ...

Issue with MaterialModule in specific modules: Element 'mat-card' is not recognized

I've searched for similar inquiries, yet none appear to address the specific issue I'm encountering. At present, my application incorporates a postModule that is lazy-loaded, while the remaining modules are traditionally loaded. All of them util ...

Errors in the Latest Release of Angular2 and Visual Studio 2015

After taking a stroll through the Angular 2 Tour of Heroes sample application with the latest Angular 2 version, I decided to host it within a Visual Studio 2015 Empty Web application. Following the Angular sample closely means that I'm not incorporat ...

Listening for value changes on a reactive form seems to be a challenge for me

While attempting to listen for value changes on a reactive form, I ran into the following error: This expression is not callable. Type 'Observable<string | null>' has no call signatures. searchWord = this.fb.group({ word: ['' ...

Is it possible to apply JavaScript object destructuring but make changes to certain values before assigning them to a new object?

After receiving movie data from an api, I am currently manually creating a new object with a subset of properties and modified values. Is there a more efficient way to achieve this using javascript/typescript object destructuring syntax? I specifically wa ...

How to Retrieve a File Using Angular 2

Currently, I am trying to download a file in pdf format using Angular 2. For this purpose, I have incorporated FileSaver.js to facilitate the saving of the file as a pdf. (response) => { var mediaType = 'application/pdf'; let pdfConte ...