I am trying to create a custom validator in model driven form,is this right way to implement it

Question

while implementing my code i am getting following errors in console

Error: Cannot find control with name: 'password' at _throwError (forms.js:1732) at setUpControl (forms.js:1640) at FormGroupDirective.push../node_modules/@angular/forms/fesm5/forms.js.FormGroupDirective.addControl (forms.js:4454) at FormControlName.push../node_modules/@angular/forms/fesm5/forms.js.FormControlName._setUpControl (forms.js:4959) at FormControlName.push../node_modules/@angular/forms/fesm5/forms.js.FormControlName.ngOnChanges (forms.js:4909) at checkAndUpdateDirectiveInline (core.js:9244) at checkAndUpdateNodeInline (core.js:10512) at checkAndUpdateNode (core.js:10474) at debugCheckAndUpdateNode (core.js:11107) at debugCheckDirectivesFn (core.js:1106

i tried to create a new form group by grouping password and repassword control,but it does not worked for me.

add-organization.ts

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


@Component({
  selector: 'app-add-organization',
  templateUrl: './add-organization.component.html',
  styleUrls: ['./add-organization.component.css']
})
export class AddOrganizationComponent implements OnInit {

     myform: FormGroup;
     passwords: FormGroup;
     organizationName: FormControl;
     organizationAddress: FormControl;
     pinCode: FormControl;
     mobileNumber: FormControl;
     organizationType: string[] = ["WholeSale","Retail"];
     businessType: FormControl;
     ownerName: FormControl;
     password: FormControl;
     rePassword: FormControl;
     telephoneNumber: FormControl;
     gstin: FormControl;




  createFormControls() {

     this.organizationName = new FormControl("", Validators.required);
     this.ownerName = new FormControl("", Validators.required);
     this.organizationAddress = new FormControl("", Validators.required);
     this.pinCode = new FormControl("", Validators.required);
     this.mobileNumber = new FormControl("", Validators.required);
     this.telephoneNumber = new FormControl();
     this.businessType = new FormControl("", Validators.required);
     this.gstin = new FormControl("", [Validators.required]);
     this.passwords = new FormGroup({
      password: this.password = new FormControl("",[Validators.required,Validators.minLength(8)]),
      repassword: this.rePassword = new FormControl("",[Validators.required])
      },{ validators: this.passwordValidator }
      )
  }

  passwordValidator(fb: FormGroup) {
    let password  = fb.controls.password.value;
    let repass = fb.controls.repassword.value; 
      if (repass !== password) {
        return {
          passwordMatch: {
            passwordMatch: password
          }
        }
      }
    return null;
  } 

  createForm() {
    this.myform = new FormGroup({
    ownerName: this.ownerName,
    organizationName: this.organizationName,
    organizationAddress: this.organizationAddress,
    pinCode: this.pinCode,
    mobileNumber: this.mobileNumber,
    telephoneNumber: this.telephoneNumber,
    businessType: this.businessType,
    gstin: this.gstin,
    }); 
  }

  onSubmit() {
    if (this.myform.valid) {
      console.log("Form Submitted!");
      console.log(this.myform.value);
      this.myform.reset();
    }
  }


  constructor() { }

  ngOnInit() {
    this.createFormControls();
    this.createForm();
  }

}

add-organization.html

    <mat-form-field>
            <input matInput placeholder="Set password" type = "password" formControlName="password">
            <mat-error *ngIf="password.errors?.required">Password is required</mat-error>
            <mat-error *ngIf="password.errors?.minlength">
                Password must be {{password.errors.minlength.requiredLength}} characters long, we need another {{password.errors.minlength.requiredLength - password.errors.minlength.actualLength}} characters
            </mat-error>
          </mat-form-field>
          <mat-form-field>
            <input  matInput placeholder="Re-Enter password" type = "password" formControlName="rePassword">
            <mat-error *ngIf="rePassword.errors?.required">Password is required</mat-error>
            <mat-error *ngIf="passwords.validators.passwordValidator">not match</mat-error>
   </mat-form-field>

i expect the out to show error message if both password and rePassword are not same else not

Answer 1

You have created the Form twice. Once, with all the controls in createFormControls(). Another in createForm(). THe createForm does not have the password field, thus it does not create a password control, hence the html throws error while creating a formControl with the name password.

What you need in the createForm() is patchValue() to update the value of the controls without changing the structure of the form.

Answer 2

it's only and advise. When you create a formGroup you can use directly

this.myform = new FormGroup({
    ownerName: new FormControl('',Validators.Required),
    organizationName: new FormControl('',Validators.Required),
    organizationAddress: new FormControl('',Validators.Required),
    pinCode: new FormControl('',Validators.Required),
    mobileNumber: new FormControl('',Validators.Required),
    telephoneNumber: new FormControl(''),
    businessType: new FormControl('',Validators.Required),
    gstin: new FormControl('',Validators.Required),
    password:new FormGroup({
      password: new FormControl("",[Validators.required,Validators.minLength(8)]),
      repassword: this.rePassword = new FormControl("",[Validators.required])
      },{ validators: this.passwordValidator }
      )
    }); 

If you use {validators:this.passwordValidator} your function is declared as

passwordValidator(formGroup:FromGroup)
{ 
     ....
}

If you use { validators: this.passwordValidator() } //<--see the ()

passwordValidator()
{
  return (formGroup:FromGroup)=>
  { 
     ....
  }
}

Answer 3

this is how I would do this:

function passwordValidator() { // wrapper fn
  return (ctrl: AbstractControl) => { // return the function w abstractControl
    const fb = ctrl as FormGroup; //type it
    const passwordCtrl  = fb.get('password'); // get the ctrls
    const repassCtrl = fb.get('repassword'); 
    if (!passwordCtrl || !repassCtrl) // handle errors!
      throw new Error('need password and repass controls');
    if (passwordCtrl.value // make sure forms have values (required error should show in this case, not pass match)
          && repassCtrl.value 
          && repassCtrl.value !== passwordCtrl.value) {
      return {
        passwordMatch: password //redunant
      }
    }
    return null;
  }
}

define that outside of your component (so it's reusable) then use like:

{ validators: [passwordValidator()] }

however, your error is really here when you build your group:

this.passwords = new FormGroup({
  password: new FormControl("",[Validators.required,Validators.minLength(8)]),
  repassword: new FormControl("",[Validators.required])
  },{ validators: [passwordValidator()] }
)

you just can't build forms the way you were doing it. you should define your password and repassword variables more like this:

get password() { return this.passwords.get('password');
get repassword() { return this.passwords.get('repassword');

to get the error to appear as you have it (inside a mat error field) then you need to add this weird thing to your component:

parentErrorMatcher = {
  isErrorState(control: FormControl): boolean {
    return control.parent.invalid && control.touched;
  }
};

then use it in template on the form field where you want to display the error:

<mat-form-field [errorStateMatcher]="parentErrorMatcher">

this will cause the error state to reflect the parent instead of the child