Versuche, eine Gesamtsumme von payOffs.amount zu berechnen (payOffs ist ein FormArray). Ich bin mir nicht sicher, wie ich es richtig machen soll, damit die Summe Änderungen an aktuellen und neuen Beträgen feststellt. Hier ist ein plnkr, den ich als Basiscode genommen habe:http: //plnkr.co/edit/nHSIsciSZNTQzQjxkXsk? p = preview

  <form (ngSubmit)="onSubmit()" [formGroup]="form">

<label>Name</label>
<input type="text" formControlName="name" [(ngModel)]="myModel.name" placeholder="Name">

<p>Pay Offs</p>
<table class="simple-table">
  <tr>
    <th>Amount</th>
    <th>Date</th>
    <th>Final?</th>
    <th></th>
  </tr>
<tbody>
  <tr *ngFor="let po of form.find('payOffs').controls; let i = index">
    <td>
      <input type="text" size=10 [formControl]="po.controls.amount" [(ngModel)]="myModel.payOffs[i].amount">
    </td>
    <td>
      <input type="text" [formControl]="po.controls.date" [(ngModel)]="myModel.payOffs[i].date">
    </td>
    <td>
      <input type="checkbox" [formControl]="po.controls.final" [(ngModel)]="myModel.payOffs[i].final">
    </td>
    <td>
      <button (click)="deletePayOff(i)" style="color: white; background: rgba(255, 0, 0, .5)">x</button>
    </td>
  </tr>
</tbody>
<tr>
  <td colspan="4" style="text-align: center; padding: .5em;">
    <button (click)="addPayOff($event)" style="color: white; background: rgba(0, 150, 0, 1)">Add Pay Off</button>
  </td>
</tr>
</table>

@Component({
  selector: 'my-app',
  templateUrl: 'app/app.html',
  directives: [REACTIVE_FORM_DIRECTIVES],
  providers:  []
})
export class AppComponent {
  form: FormGroup;
  myModel:any;

  constructor() {
    // initializing a model for the form to keep in sync with. 
    // usually you'd grab this from a backend API
    this.myModel = {
      name: "Joanna Jedrzejczyk",
      payOffs: [
        {amount: 111.11, date: "Jan 1, 2016", final: false},
        {amount: 222.22, date: "Jan 2, 2016", final: true}
        ]
    }

    // initialize form with empty FormArray for payOffs
    this.form = new FormGroup({
      name: new FormControl(''),
      payOffs: new FormArray([])
    });

    // now we manually use the model and push a FormGroup into the form's FormArray for each PayOff
    this.myModel.payOffs.forEach( 
      (po) => 
        this.form.controls.payOffs.push(this.createPayOffFormGroup(po))
    );
  }

  createPayOffFormGroup(payOffObj) {
    console.log("payOffObj", payOffObj);
    return new FormGroup({
      amount: new FormControl(payOffObj.amount),
      date: new FormControl(payOffObj.date),
      final: new FormControl(payOffObj.final)
    });
  }

  addPayOff(event) {
    event.preventDefault(); // ensure this button doesn't try to submit the form
    var emptyPayOff = {amount: null, date: null, final: false};

    // add pay off to both the model and to form controls because I don't think Angular has any way to do this automagically yet
    this.myModel.payOffs.push(emptyPayOff);
    this.form.controls.payOffs.push(this.createPayOffFormGroup(emptyPayOff));
    console.log("Added New Pay Off", this.form.controls.payOffs)
  }

  deletePayOff(index:number) {
    // delete payoff from both the model and the FormArray
    this.myModel.payOffs.splice(index, 1);
    this.form.controls.payOffs.removeAt(index);
  }
}