Angular 2 equal-validator.directive.ts

equal-validator.directive.ts

import { Directive, forwardRef, Attribute } from '@angular/core';
import { Validator, AbstractControl, NG_VALIDATORS } from '@angular/forms';

// variation from https://plnkr.co/edit/KgjSTj7VqbWMnRdYZdxM?p=preview

@Directive({
    selector: '[validateEqual][formControlName],[validateEqual][formControl],[validateEqual][ngModel]',
    providers: [
        { provide: NG_VALIDATORS, useExisting: forwardRef(() => EqualValidator), multi: true }
    ]
})
export class EqualValidator implements Validator {
    constructor(@Attribute('validateEqual') public validateEqual: string,
                @Attribute('reverse') public reverse: string,
    ){}

    validate(c: AbstractControl): { [key: string]: any } {
      let other = c.root.get(this.validateEqual);
      if (!other) return null;
      return this.reverse === 'true' ? 
        this.validateReverse(c, other) : this.validateNoReverse(c, other);
    }

    validateNoReverse(c: AbstractControl, other: AbstractControl): { [key: string]: any } {
      return other.value === c.value ?
        null : {validateEqual: true}
    }

    validateReverse(c: AbstractControl, other: AbstractControl): { [key: string]: any } {
      if (c.value === other.value) {
        delete other.errors['validateEqual'];
        if (Object.keys(other.errors).length == 0) {
          other.setErrors(null);
        };
      } else {
        other.setErrors(Object.assign(other.errors,  {validateEqual: true}));
      }

      return null;
    }
}