Display custom validator error with mat-error

Question

I come to you for talking about a problem with angular material. In fact, I think it\'s an issue, but I prefer looking for a misunterstanding first.

The first thing abou

Answer 1

How to create a custom validation:

if the internal property 'isValid' of the component is false, then set the input status in error, and display a message.

HTML:

Input not valid.

TS:

isValid = true;

changeValitationStatus() {
this.matcher = new InputErrorStateMatcher(!this.isValid);
}

matcher = new InputErrorStateMatcher(!this.isValid);



class InputErrorStateMatcher implements ErrorStateMatcher {
    constructor(private errorstate: boolean) {}
    isErrorState(control: FormControl|null, form: FormGroupDirective|NgForm|null):boolean {
    return this.errorstate;
  }
}

And in this way you have a validation using only the formControl.