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

obsessiveprogrammer's answer was correct for me, however I had to change the childrenEqual function with angular 6 and strictNullChecks (which is an option recommended by the angular team) to this:

static childrenEqual: ValidatorFn = (control: AbstractControl): ValidationErrors | null => {
        const f = control as FormGroup;

        const [firstControlName, ...otherControlNames] = Object.keys(f.controls || {});

        if(f.get(firstControlName) == null) {
            return null;
        }

        otherControlNames.forEach(controlName => {
            if(f.get(controlName) == null) {
                return null;
            }
        })

        const isValid = otherControlNames.every(controlName => f.get(controlName)!.value === f.get(firstControlName)!.value);
        return isValid ? null : { childrenNotEqual: true };
    }