Steps to create a formGroup in Angular 12

Question

Steps to create a formGroup in Angular 12

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

@Component({
  selector: 'app-signup',
  templateUrl: './signup.component.html',
  styleUrls: ['./signup.component.css']
})
export class SignupComponent implements OnInit {
  signupForm: FormGroup | undefined;
  constructor(public formBuilder: FormBuilder) {
    
   }
 


ngOnInit(): void {
    this.signupForm = this.formBuilder.group({
      username:[' ', Validators.required],
      email:[' ', Validators.required],
      password:[' ',[Validators.required]]
    })
  }
}

Additionally, there is a coding issue:

src/app/auth/signup/signup.component.ts:6:16 6 templateUrl: './signup.component.html', ~~~~~~~~~~~~~~~~~~~~~~~~~ An error has been detected in the template of component SignupComponent.

Error: src/app/auth/signup/signup.component.html:40:110 - error TS2531: Object is possibly 'null'.

40 <span *ngIf="!signupForm.get('password').valid && signupForm.get('password').touched"> ~~~~~~~

src/app/auth/signup/signup.component.ts:6:16 6 templateUrl: './signup.component.html', ~~~~~~~~~~~~~~~~~~~~~~~~~ An error has occurred in the template of component SignupComponent.

Error: src/app/auth/signup/signup.component.ts:10:3 - error TS2564: Property 'signupForm' has no initializer and is not definitely assigned in the constructor.

angular typescript

Answer 1

Answer №1

To correct the issue, you can either eliminate '| undefined' or adjust your span as shown below (with null protection)

<span *ngIf="!signupForm?.get('password')?.valid && signupForm?.get('password')?.touched">

Answer 2

To correct the issue, you can either eliminate '| undefined' or adjust your span as shown below (with null protection)

<span *ngIf="!signupForm?.get('password')?.valid && signupForm?.get('password')?.touched">

Answer 3

Answer №2

There are a couple of mistakes in your code that need to be addressed.

First Mistake

The first mistake is related to the placement of your form builder code. It should not be inside the ngOnInit method, but rather at the top of your declaration. Here's how you can correct it:

export class SignupComponent implements OnInit {
 signupForm = this.formBuilder.group({
    username: ['', Validators.required],
    email: ['', Validators.required],
    password: ['', [Validators.required]]
  })
}
 constructor(public formBuilder: FormBuilder) {

 }



ngOnInit(): void { }
}

The ngOnInit lifecycle method is called after the component is created by the constructor, but before it gets rendered or any other lifecycle methods are executed. Any initialization done here may result in null or undefined values until Angular completes this method execution.

Therefore, placing the form builder outside of ngOnInit ensures that the component always has a complete form object during its creation process, eliminating the possibility of calling a method on an undefined or null object from the template.

Second Mistake

The second mistake stems from missing '?' operators in your method calls following 'get' operations. The '.get' method could potentially return a null value if the specified field doesn't exist. Hence, adding a '?' after the '.get' signals that the subsequent operation may not have a valid object to work with.

Answer 4

There are a couple of mistakes in your code that need to be addressed.

First Mistake

The first mistake is related to the placement of your form builder code. It should not be inside the ngOnInit method, but rather at the top of your declaration. Here's how you can correct it:

export class SignupComponent implements OnInit {
 signupForm = this.formBuilder.group({
    username: ['', Validators.required],
    email: ['', Validators.required],
    password: ['', [Validators.required]]
  })
}
 constructor(public formBuilder: FormBuilder) {

 }



ngOnInit(): void { }
}

The ngOnInit lifecycle method is called after the component is created by the constructor, but before it gets rendered or any other lifecycle methods are executed. Any initialization done here may result in null or undefined values until Angular completes this method execution.

Therefore, placing the form builder outside of ngOnInit ensures that the component always has a complete form object during its creation process, eliminating the possibility of calling a method on an undefined or null object from the template.

Second Mistake

The second mistake stems from missing '?' operators in your method calls following 'get' operations. The '.get' method could potentially return a null value if the specified field doesn't exist. Hence, adding a '?' after the '.get' signals that the subsequent operation may not have a valid object to work with.

Steps to create a formGroup in Angular 12

Answer №1

Answer №2

First Mistake

Second Mistake

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