Angular reactive form validator for value different than X

Question

I'm using Angular Reactive form in my Angular app and i have a <select> input where the default value if -1, by setting Validators.required even if the value is still -1 it will be accepted, so how could i make a validator to accept the value if is valid and is != -1?

I was trying to do something like this but it's not working:

coperti: new FormControl(-1, [Validators.required, Validators.pattern(`[\d]`)]),

Християн Христов Християн Христов · Accepted Answer · 2020-11-17T16:47:51

You can create a custom validator:

form = new FormGroup({
    coperti: new FormControl("", [
      (c) => {
        // Here the c is your form control and we check if the  value is -1 or 0
        if (c.value === -1 || c.value === 0) {
        // if the condition is met we return the error
          return { wrong: true };
        }
        // if the condition isn't met (e.g. the form is valid) we return null, which
        // will not apply errors on the form control
        return null;
      }
    ])
  });

All validators are simple functions so feel free to create whatever custom validator when needed, don't limit yourself only to the build in ones.

Angular reactive form validator for value different than X

1 Answers