ionic2:如何在表单中进行计算？

<ion-content>
  <ion-list>
    <ion-item>
      <ion-label>数值1</ion-label>
      <ion-input type="number" [(ngModel)]="value1"></ion-input>
    </ion-item>
    <ion-item>
      <ion-label>数值2</ion-label>
      <ion-input type="number" [(ngModel)]="value2"></ion-input>
    </ion-item>
    <ion-item>
      <ion-label>结果</ion-label>
      <ion-input type="number" [value]="result" disabled></ion-input>
    </ion-item>
  </ion-list>
</ion-content>

import { Component } from '@angular/core';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  value1: number;
  value2: number;
  result: number;

  calculate() {
    this.result = this.value1 + this.value2;
  }
}