Angular 6 Required only one field from many fields

Question

I am new in angular. I have one scenario where I need only one field required from 5 fields in the form, means if the user fills at least one field then form makes valid.

Thanks in advance.

Answer 1

    <form [formGroup]="formdata">
<div class="form-group">
    <label for="fieldlabel1">fieldLabel1</label>
    <input type="text" id="fieldlabel1" formControlName="fieldName1" class="form-control"><br>
    <label for="fieldlabel2">fieldLabel2</label>
    <input type="text" id="fieldlabel2" formControlName="fieldName2" class="form-control">
</div>
 </form>

<div class="row">
      <div class="col-sm-12">
        <button type="submit" value="submit" (click)="somefunctioncall()" [disabled]="formdata.invalid">
          Submit
        </button>
      </div>
</div>



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

export class test {

formdata: FormGroup;

 ngOnInit() {


  this.formdata = new FormGroup({

      fieldName1: new FormControl("", Validators.compose([
        Validators.required
      ])),
      fieldName2: new FormControl("", Validators.compose([
        // remove required validation for one you dont need.
      ]))
    })   
 }
}

Answer 2

Check this example of phone number validator

import { FormGroup, FormBuilder, Validators } from '@angular/forms';
import { NumberValidator } from '../validators/form-validators';


constructor(
    private fb: FormBuilder){}

FormName: FormGroup = this.fb.group({
    phoneNumber: ['', NumberValidator]    
  });

in form-validator file

import { AbstractControl, ValidatorFn } from '@angular/forms';

export const NumberValidator = (): ValidatorFn => {
  return (control: AbstractControl): { [key: string]: any } | null => {
    const mobileRegex = /^[()-\d\s]*$/g;
    const result = mobileRegex.test(control.value);
    return result ? null : { mobileInvalid: { value: control.value } };
  };
};

let me know if you have any doubts.

Answer 3

Since you need to check for the validity of whole form only if one of the fields is non empty , You can manually set the validity like below :

if(!this.valid){
    this.form.setErrors({ 'invalid': true});
}else{
    this.form.setErrors(null);
}

Where this.valid is your condition based on which you can set the validity

You can check the example : https://angular-exmphk.stackblitz.io

You can also check the answer : FormGroup validation in "exclusive or" which does form validation based on some condition

Hope this helps