I have an Angular 2 application that uses the `ReactiveForms` module to manage a form that uses a custom validator. The validator receives a `FormControl` object. I have a few input fields that could use the same custom validator if only I knew the name of the field when the `FormControl` was passed to the validator.

I can't find any method or public property on `FormControl` that exposes the input field's name. It's simple enough to see its value, of course. The following shows how I would like to use it:

```
public asyncValidator(control: FormControl): {[key: string]: any} {
  var theFieldName = control.someMethodOfGettingTheName(); // this is the missing piece

  return new Promise(resolve => {
      this.myService.getValidation(theFieldName, control.value)
        .subscribe(
          data => {
            console.log('Validation success:', data);
            resolve(null);
          },
          err => {
            console.log('Validation failure:', err);
            resolve(err._body);
          });
    });
  }

```