Encountering an Issue: The formGroup function requires an instance of a FormGroup. Kindly provide one

I am a beginner with Angular 2 and despite reviewing numerous stack overflow answers, I still can't resolve my issue.

I have recently started learning about angular reactive forms and wanted to try out my first example but I'm facing some difficulties. Any assistance would be greatly appreciated.

Here is the HTML form code:

<div class="container">
  <div class="row">
    <div class="col-xs-12 col-sm-10 col-md-8 col-sm-offset-1 col-md-offset-2">
      <form [formGroup]="signupForm" (ngSubmit)="onSubmit()">
        <div id="user-data">
          <div class="form-group">
            <label for="username">Username</label>
            <input
              type="text"
              id="username"
              formControlName="username"
              class="form-control">
          </div>
          <div class="form-group">
            <label for="email">Email</label>
            <input
              type="email"
              id="email"
              formControlName="email"
              class="form-control">
          </div>
          <div class="radio" *ngFor="let gender of genders">
            <label>
              <input
                type="radio"
                class="form-control"
                formControlName="gender"
                [value]="gender">{{ gender }}
            </label>
          </div>
        </div>
        <button class="btn btn-primary" type="submit">Submit</button>
      </form>
    </div>
  </div>
</div>

And here is the TS file code:

import { Component, OnInit } from '@angular/core';
import { FormGroup } from '@angular/forms';
import { FormControl } from '@angular/forms';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})

export class AppComponent implements OnInit {

  genders = ['male', 'female'];
  
  signupForm: FormGroup;

  ngOnInit() {
    
    this.signupForm = new FormGroup({
      
      'username': new FormControl(null),
      'email': new FormControl(null),
      'gender': new FormControl('male')
    });
  }

  onSubmit() {
    console.log(this.signupForm);
  }
}

When I check the output, I notice that the Gender field is not displaying along with Username and Email fields.

If you could assist me in fixing this minor issue, I would greatly appreciate it as I seem to be stuck on it.

Answer №1

In my experience, I encountered a situation where I was utilizing Reactive Forms and fetching data for the form asynchronously from a service. However, the generation of the form template began concurrently. Consequently, the form would initially be undefined as it would only be constructed after receiving the data from the API call. Therefore, it is crucial to first verify whether the form has been initialized before commencing the template generation.

<form class="col-sm-12 form-content" *ngIf="form" [formGroup]="form">

Answer №2

Error encountered: formGroup expects a FormGroup instance
indicates that you forgot to instantiate the FormGroup named signupForm in your template.

To resolve this issue, you need to create an instance for signupForm as shown below:

this.signupForm = new FormGroup({
  // Define form controls here
  'username': new FormControl(null),
  'email': new FormControl(null),
  'gender': new FormControl('male')
});

Answer №3

It is important to review your component code thoroughly. It seems that the variable you declared does not match the one specified in your template.

I recommend updating the reference from sigupForm to signupForm.

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