Validator with Inputs

validator.component.ts

import { Component, Input, OnInit } from '@angular/core';
import { FormControl, FormGroup, ValidationErrors } from '@angular/forms';
import { TranslateService } from '@ngx-translate/core';

@Component({
  selector: 'app-validator',
  templateUrl: './validator.component.html',
  styleUrls: ['./validator.component.scss']
})
export class ValidatorComponent implements OnInit {
  @Input() public control: FormControl;
  @Input() public customName: string;
  @Input() public customValidation: { name: string, text: string };
  public name: string;

  constructor(private translateService: TranslateService) {
  }

  public ngOnInit(): void {
    const fieldName = this.customName ? this.customName : this.getControlName();

    this.name = this.translateService.instant(`fields.${fieldName}`);
  }

  /**
   * Check if the validator has a custom validation message
   *
   * @param errors
   *
   * @return string
   */
  public message(errors: ValidationErrors | null): string {
    const properties = Object.keys(errors);
    let customMessage: boolean;

    if (this.customValidation) {
      customMessage = (properties.indexOf(this.customValidation.name) > -1);
    }

    return customMessage ? this.customValidation.text : `validators.${properties[0]}`;
  }

  /**
   * Extract control name from formGroup
   *
   * @return string
   */
  public getControlName(): string {
    let controlName = null;
    const parent = this.control['parent'];

    if (parent instanceof FormGroup) {
      for (const name in parent.controls) {
        if (this.control === parent.controls[name]) {
          controlName = name;
        }
      }
    }

    return controlName;
  }
}