ng-bootstrap datepicker validity and initial value

问题

using the datepicker component in a template-driven form like so:

        <input
          class="form-control"
          placeholder="dd-mm-yyyy"
          ngbDatepicker
          #from="ngbDatepicker"
          (click)="from.toggle()"
          [(ngModel)]="params.from"
          name="from"
          required
        />

how would I go about getting the validity? {{from.invalid}} doesn't return anything.

Also, how would I set the initial state? tried:

new Date()

{
  year: 2017,
  month: 10,
  day: 20
}

Simple string like 2017-10-20 and 20-10-2017 (matching my format).

来源：https://stackoverflow.com/questions/46693926/ng-bootstrap-datepicker-validity-and-initial-value