reactive form custom validators not displaying the error in angular6

Question

In this demo i have created a sample form for custom validator, here i have From date and TO date and from time and To time, working fine: For from date and to date validation working fine and showing error messages.

problem: when choosing same date , eg) july 21 2018 as from date and same in To date and In from Time be 4:00 Am and To Time be 3:00AM, the condition gets satisfied, but which is not showing an error message.Somethis went wrong in implementation,can anyone help me to solve appreciated

In html i have given validation message but which gets not displayed.

To Time:
<input type="time" formControlName="ToTime">
    <mat-error *ngIf="DaterForm.get('ToTime').hasError('InValidToTime')">FromTime Should be less than ToTime if choose a same date</mat-error>

In component:

 DaterForm : FormGroup;

constructor(private fb:FormBuilder){
}
   ngOnInit(){

 this.DaterForm = this.fb.group(
{
  FromDate:['',[AppCustomDirective.fromDateValidator]], // validation working fine
  FromTime:[''],
  ToDate:['',[AppCustomDirective.ToDateValidator]],// validation working fine
  ToTime:['']
},{validator:[AppCustomDirective.timeValidator] // validation not working
}

Custom validation:

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

export class AppCustomDirective extends Validators{

   static fromDateValidator(fdValue: FormControl) {
    const date = fdValue.value;
    console.log('x');
    if (date ===null || date==='') return { requiredFromDate: true };

  }

   static ToDateValidator(todValue: FormControl) {
    const date = todValue.value;

    if (date ===null || date==='') return { requiredToDate: true };

  }


  static timeValidator(formGroupValues: FormGroup): any {
    debugger;
    console.log(formGroupValues);
    const FromDate = formGroupValues.get('FromDate').value;
    const ToDate = formGroupValues.get('ToDate').value;
    const FromTime = formGroupValues.get('FromTime').value;
    const ToTime = formGroupValues.get('ToTime').value;

    if (FromDate.toString() === ToDate.toString()) {
      let fromTime = [];
      let toTime = [];
      fromTime = FromTime.split(':');
      toTime = ToTime.split(':');
      if (parseInt(fromTime[0]) > parseInt(toTime[0])){
      alert("condition satisfied not return any error message");
         return { InValidToTime: true };
        }
      else if (
        parseInt(fromTime[0]) === parseInt(toTime[0]) &&
        parseInt(fromTime[1]) > parseInt(toTime[1])
      ){  alert("condition satisfied not return any error message")
        return { InValidToTime: true };
      }
    }
  }
}

live demo

Answer 1

Its because you are setting errors on your form while you expect for error to be on particular input.

Changing to <mat-error *ngIf="DaterForm.hasError('InValidToTime')"> Fixes the issue.

FYI this is not how mat-error is designed to be used with <input matInput/>

https://stackblitz.com/edit/angular-customvalidator-1fu5vx?file=app/datepicker-overview-example.html