AngularJS指令手表有效性 [英] AngularJS directive watch validity

问题描述

我尝试创建应[执行某些动作时输入字段被标记为无效指令。对于这个例子让我们假设我有一个指令，它会检查，如果输入的是一个素数，我想创建一个指令，它增加了一个类元素时，它的无效：

I try to create a directive which should peform some actions when an input field is marked as invalid. For this example lets assume I have a directive which checks if the input is a prime number, and I want to create a directive which adds a class to the element when it's invalid:

<input type="text" ng-model="primeNumber" validate-prime invalid-add-class="error">

在验证贷使用在NG-模型解析器和格式化程序来更新模型的有效性。

The validate-prime uses the parsers and formatters on ng-model to update the validity of the model.

现在我想无效相加级指令添加类错误当模特是无效的，而当它是有效的将其删除。换句话说，应该看$模型控制器的有效（或$无效）属性。不过，我可以不知道如何得到这个工作。我想：

Now I want the invalid-add-class directive to add the class "error" when the model is invalid, and to remove it when it is valid. In other words, it should watch the $valid (or $invalid) property of the model controller. However, I can't figure out how to get this working. I tried:

link : function(scope, element, attrs, ctrl) {
    ctrl.$watch("$valid", function(newVal, oldVal) {
    //never fired
    });
}

也许我可以观看范围的一些变量，但我不知道，守候在变。

Perhaps I could watch some variable on scope, but I don't know which variable to watch for.

所以，我怎么能通知时模型更改的有效性？

So how can I be notified when the validity of a model changes?

推荐答案

如果你有一个＆LT;形式＆GT; ，添加一个名称到它（让我们假设'myForm的'）和名称您输入（让我们假设 myInput ）。你应该能够 $观看这个是：

If you have a <form>, add a name to it (lets assume 'myForm') and a name to your input (lets assume myInput). You should be able to $watch this by:

scope.$watch('myForm.myInput.$valid', function(validity) {})

如果你没有一个格式，你可以随时观看的功能。通过这种方式：

If you don't have a form, you can always watch a function. This way:

scope.$watch(function() { return ctrl.$valid; }, function(validity){});

您可以阅读更多有关表格的方式这里。

You can read more about the form approach here.

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