checking form control input for errors by using it as a variable

Question

I'm using angular 8 with angular material to write my website.

I have a form with formGroup created and I want to be able to use *ngIf to check for validation errors by using the actual input element as a parameter.

currently this is my working code:

I have the following form:

<form [formGroup]="queryForm" (submit)="runQuery()">
...
  <mat-form-field>
            <input matInput #timezone placeholder="Timezone" aria-label="Timezone" formControlName="timePeriodTimeZone"/>
            <mat-hint>timezone as a number</mat-hint>
            <mat-error *ngIf="hasError('timePeriodTimeZone','required')">timezone required</mat-error>
        </mat-form-field>
...
</form>

and in the class of the component I implemented the hasError() function like this:

 public hasError = (controlName: string, errorName: string) =>{
    return this.queryForm.controls[controlName].hasError(errorName);
  }

and of course I configured the queryForm variable as a group created by form builder.

is there a way to check the error without calling a function from the class itself?

since I added #timezone to the input field I assumed i will be able to do something like:

<mat-error *ngIf="timezone.hasError('required')">timezone required!</mat-error>

but I can't! :)

I would prefer to use something like that cause I want to create an error handling component with some mat-errors so I will be able to reuse it in each input field and I would like to paste to it the input control instead of the entire form group.

any information regarding this issue would be greatly appreciated.

thanks!

ufk · Accepted Answer · 2019-07-16 12:27:06Z

1

you know that if the field has a unique validator, you can use simply

<mat-error>timezone required!</mat-error>

(the *ngIf is not necesary).

if you want has a big control of errors, you can has some like

<mat-error >{{getError('timezone')}}</mat-error>

and you has a function like

getError(field:string)
{
   const control=this.myForm.get(field);
   string error=''
   switch (field)
    case 'timezone':
       error=control.hasError('required')?'time zone required':
              control.hasError('other')?' other error':''
    break;
    case '....'
   }
   return error;
}

edited Jul 16, 2019 at 12:27

ufk

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answered Jul 16, 2019 at 12:08

Eliseo

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