Error TS2531 object is possibly null in angular reactive forms

Question

Hi i have tried to do reactive form validation in angular 11 but its showing following error in terminal.

error TS2531 object is possibly null.

my code in signup.component.ts

import {FormGroup, FormControl, Validators} from '@angular/forms';
        
form =  new FormGroup({
    firstName: new FormControl('',Validators.required)
})
    
get f()
{
    return this.form.controls;
}

in signup.component.html

<form role="form" [formGroup]="form">
    <div class="form-group">
        <label>Name</label>
        <input type="text" name="name" class="form-control" formControlName="firstName" [ngClass]="{'is-invalid':form.get('firstName').touched && form.get('firstName').invalid}">
        <div *ngIf="f.firstName.touched && f.firstName.invalid">
            <small class="text-danger" *ngIf="f.firstName.errors.required">
                Name is required!
            </small>
            
        </div>
    </div>
</form>

when i run its showing error in

<small class="text-danger" *ngIf="f.firstName.errors.required"> Name is required!

error TS2531 object is possibly null.

Answer 1

latest version of angular requires you Use the safe navigation operator inside your first if check as well eg.

*ngIf="f.firstName?.touched && f.firstName?.invalid"

then finally

*ngIf="f.firstName.errors?.required"

Answer 2

The object f.firstName.errors can be null. Use the safe navigation operator ?:

*ngIf="f.firstName.errors?.required"

Answer 3

<div *ngIf="f.firstName?.touched && f.firstName?.invalid">
<small class="text-danger" *ngIf="f.firstName?.errors?.['required']">

Doing validation in reactive form Angular 13 requires to add optional chaining operator (the question mark '?') to the FormControl object (f.firstName) and its errors property.

Answer 4

<div *ngIf="postForm.get('title')?.touched && !postForm.get('title')?.valid"> <div *ngIf="postForm.get('title')?.errors?.['required']" class="alert alert-warning"> Title is required </div> </div> angular version is 13.3.0 5

The Object is possibly 'null' error can happen due to strict type checking and can be solved in 2 ways:

• Either assert that you are absolutely sure that can never be null, by using the ! (not null assertion operator)
• Use the ? (optional chaining operator) to stop an eventual error from happening in case the object is indeed null

So you can replace the if statement with postForm.get('title')?.touched && !postForm.get('title')?.valid and it should work.