Require one from two fields using Angular 2

Question

I\'m trying to create a contact form. The form looks like this:

Answer 1

I created a custom validator directive:

import {
    FormGroup,
    ValidationErrors,
    ValidatorFn,
    Validators,
  } from '@angular/forms';

  export const atLeastOne = (validator: ValidatorFn, controls:string[] = null) => (
    group: FormGroup,
  ): ValidationErrors | null => {
    if(!controls){
      controls = Object.keys(group.controls)
    }

    const hasAtLeastOne = group && group.controls && controls
      .some(k => !validator(group.controls[k]));

    return hasAtLeastOne ? null : {
      atLeastOne: true,
    };
  };

To use it, you just do this:

this.form = this.formBuilder.group({
            name: ['', Validators.required],
            email:[''],
            telefone:[''],
            message:['', Validators.required],
        }, { validator: atLeastOne(Validators.required, ['email','telefone']) });

So email or telefone would be required here. If you leave it empty then any control with a value is fine and you can use it with any type of validator, not just Validators.required.

This is reusable in any form.