角2表单验证无法使用哈希表单元素

Question

I have one form validation using angular 2.[Angular 2 Only] How to start validation part using below the way?

app.component.html:

<form   #registrationForm="ngForm"  (ngSubmit)="submitform()">
  <input type="text" class="form-control" name="name" formControlName="name" />
</form>

app.component.ts:

import { Component, Input, OnInit } from '@angular/core';
import { FormBuilder,FormGroup,Validators } from '@angular/forms';

export class AppComponent implements OnInit {
  ngForm: FormGroup;
  ngOnInit() {
    this.ngForm = this._fb.group({
      name: ['Select', Validators.required]
    });
  }
  submitform() {
    this.formSubmitted = true;
    if (!this.ngForm.valid) {
      alert("Form Not valid");
    } else {
      alert("Valid");
    }
  }
}

Above the script is not working..Where i did mistake?

Answer 1

There's an Issue with your Template. Instead of using #registrationForm="ngForm" use [formGroup]="ngForm"

You're using a Reactive Form approach and in that, to map the form on the template, with the form on the Component, you use [formGroup] on the form tag in your template.

#registrationForm="ngForm" is generally used in the Template Drive strategy of building forms. Then on (submit) you also pass the form to the method which isn't really required in this case.

Also, you should be using (submit) instead of (ngSubmit)

Try this:

<form [formGroup]="ngForm" (submit)="submitform()">
  <input type="text" class="form-control" name="name" formControlName="name" />
  <button>Submit</button>
</form>

Here's a Sample StackBlitz for your ref.

Answer 2

what are you trying to validate? there is only one input field, if you want to validate that try putting 'required' attribute or condition to validate on the input field. Also, if you need to take a look at simple form validation example, check the following repo: https://github.com/alokstar/Angular4FormValidation

Hope it helps!