`How to fix errors in template-driven forms in Angular 8`

In my template-driven form, I am encountering the following error:

ERROR TypeError: Cannot read property 'invalid' of undefined  

I am unsure why this error is happening. How can I resolve this issue?

Here is my app.component.html code:

<form name="form" (ngSubmit)="f.form.valid && onSubmit()" #f="ngForm" novalidate>
<div class="form-group">
                <label for="categoryName">Category Name:</label>
                <input type="text" class="form-control" name="categoryName" [(ngModel)]="cate.categoryName" minlength="5" #categoryname="ngModel" [ngClass]="{ 'is-invalid': f.submitted && categoryName.invalid }" required/>
                <div *ngIf="f.submitted && categoryName.invalid" class="invalid-feedback">
                    <div *ngIf="categoryName.errors.required">
                        Category Name is required
                    </div>
                </div>
                <div *ngIf="categoryName?.touched && categoryName?.errors.minlength" class="invalid-feedback">
                    Category Name must be at least 5 characters long.
                </div>
            </div>
</form>

And here is my app.component.ts code:

  cate: any = {}; 
  onSubmit() {
      alert(this.cate.categoryName);
  }

Answer №1

Within your template:

categoryName.invalid

It appears that categoryName is being used without being defined anywhere.

A possible solution could be:

 categoryName?.invalid

It's important to note that #categoryname and categoryName are different due to the use of lower case and upper case letters ("n").

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