Angular2表单验证错误

Question

Here is a simplistist form:

<form [ngFormModel]="myForm">
        <input type="text" [ngFormControl]="fname" placeholder="First Name"/>
        <div *ngIf="fname.errors.minlength">First name should be atleast 2 characters</div>
      </form>

it should display an error when the input < 2 character

The issue: When you first type in a character, the error shows up. The minute you type in the second character, there are a whole bunch of console errors

Can't quiet understand why this is happening.

see plnkr here: http://plnkr.co/edit/XUsUJzsc791oiuDDo0Pd?p=preview

Answer 1

I assume if the FormControl does not contain any errors, fname.errors is undefined . This would be the case when you have entered at least 2 characters. ngIf , however, is evaluated periodically, so accessing minlength of undefined throws the exception.

If you edit your plunkr like this, the code works:

*ngIf="fname.errors?.minlength"