Watch form validity from controller

问题

I have a form within my controller. I'd like to be able to set a scope variable based on the validity of this form. I've given the form a name already:

<div ng-controller="myCtrl">

    ...

    <form name='myForm'>
        ...
    </form>

    ...

</div>

And have created a $watch on that form's $valid property (this is located in the controller which contains this form):

$scope.$watch('myForm.$valid', function(oldVal, newVal) {
    console.log("Woo! This might be working!");
    if (newVal) {
        $scope.otherVar = true;
    } else {
        $scope.otherVar = false;
    }
}

My log statement ONLY appears on page load, but not when the form's validity changes. (I've verified that the form's $valid property is changing by inserting:

{{ myForm.$valid }}

within the scope of my form)

I've been looking around SO and from what I've seen this should be working. (Obviously something is wrong though...)

回答1:

I think your problem is function(oldVal, newVal) should be function(newVal, oldVal). Apart from that I can't find any fault in your code. Here's a working plunkr example: http://plnkr.co/edit/ur42HFcVQbpTEBkRBtdY?p=preview

Outside of that it's probably something else in your code affecting the form, you don't have it nested in something like an ng-if or ng-view?

来源：https://stackoverflow.com/questions/25027876/watch-form-validity-from-controller