Input in *ngFor can not type smoothly Angular 2

问题

Below link is a sample code.

https://plnkr.co/edit/xmWMm0yjFemdXQzZpJad?p=preview

I have an object(test), which contain a number array(test.arr).

<div *ngFor="let v of test.arr; let i = index">
    <input [(ngModel)]="test.arr[i]" type="text">
</div>

Once I type something on input, it will missing focus.

BTW, the reason why using test.arr[i] rather than v, see "Cannot assign to a reference or variable!"

回答1:

Plunker example

If you use *ngFor with primitive values number, string, ... you need to take care Angular is able to track identity.

You can use a custom trackBy function like:

<div *ngFor="let v of test.arr; let i = index;trackBy:trackByIdx">

trackByIdx(index, val) {
  return index;
}

来源：https://stackoverflow.com/questions/42200061/input-in-ngfor-can-not-type-smoothly-angular-2