由于AngularJS中用来取代<form>的ng-form指令可以嵌套，并且外部表单在所有子表单都合
法之前一直处于不合法状态，因此我们可以在动态生成子表单的同时使用表单验证功能。是的，
鱼和熊掌可以兼得。
<!doctype html>
<html ng-app="myApp">
<head>
<link rel="stylesheet" href="//cdn.jsdelivr.net/foundation/4.3.2/css/foundation.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.0-rc.2/angular.js"></script>
</head>
<body>
<form name="signup_form" ng-controller="FormController" ng-submit="submitForm()" novalidate>
<div ng-repeat="field in fields" ng-form="signup_form_input">
<input type="text"
name="dynamic_input"
ng-required="field.isRequired"
ng-model="field.name"
placeholder="{{field.placeholder}}" />
<div ng-show="signup_form_input.dynamic_input.$dirty && signup_form_input.dynamic_input.$invalid">
<span class="error" ng-show="signup_form_input.dynamic_input.$error.required">The field is required.</span>
</div>
</div>
<button type="submit" ng-disabled="signup_form.$invalid">Submit All</button>
</form>
</body>
</html>
input.ng-invalid {
border: 1px solid red;
}
input.ng-valid {
border: 1px solid green;
}
angular.module('myApp', [])
.controller('FormController', function($scope) {
$scope.fields = [
{placeholder: 'Username', isRequired: true},
{placeholder: 'Password', isRequired: true},
{placeholder: 'Email (optional)', isRequired: false}
];
$scope.submitForm = function() {
alert("it works!");
};
});