Angularjs使用指令做表单校验的方法

<form class="form-horizontal" name="form" role="form" ng-controller="ValidCtrl">
 <div class="form-group">
  <label for="user" class="col-sm-2 control-label" >用户名</label>
  <div class="col-sm-5">
   <input type="text" ng-model="user" name="user" id="user" user-validator class="form-control" required="required">
  </div>
  <label class="col-sm-5" ng-show="form.user.$pristine">请输入用户名</label>
  <label class="col-sm-5" ng-show="form.user.$error.required && form.user.$dirty">
   用户名不能为空
  </label>
  <label class="col-sm-5" ng-show="form.user.$error.defined && form.user.$dirty">
   用户名不符合规则
  </label>
  <label class="col-sm-5" ng-show="form.user.$valid && form.user.$dirty">
   用户名有效
  </label>
 </div>
</form>

angular.module('shuffleApp', [])
 .directive('userValidator', ['$log', function($log) {
   return {
     restrict: 'A',
     require: 'ngModel',
     link: function($scope, $element, $attrs, $ngModelCtrl) {
       var verifyRule = [/^\d+$/, /^[a-z]+$/, /^[A-Z]+$/];
       var verify = function(input) {
         return !(verifyRule[0].test(input) || 
              verifyRule[1].test(input) || 
              verifyRule[2].test(input));
       };
       $ngModelCtrl.$parsers.push(function(input) {
         var validity = verify(input);
         $ngModelCtrl.$setValidity('defined', validity);
         return validity ? input : false;
       });
       $ngModelCtrl.$formatters.push(function(input) {
         var validity = verify(input);
         $ngModelCtrl.$setValidity('defined', validity);
         return validity ? input : false;
       })
     }
   }
  }]);