有这样的一个需求：添加用户的时候，根据主键判断当前添加用户的email是否已经被使用。
为此，我们需要把主键和email来传递给远程的一个API，让API返回结果，告之当前email是否被使用过。
写一个验证email唯一性的Directive，页面大致如下表现：
<input type="text" name="email" class="form-control"data-ng-model="vm.customer.email"data-ng-model-options="{updateOn: 'blur', allowInvalid: true}"data-my-uniquedata-my-unique-key="{{vm.customer.id}}"data-my-unique-property="email"data-ng-minlength="3"required /><span class="errorMessage" ng-show="editForm.email.$touched && editForm.email.$error.unique">Email already in use </span>
以上，data-my-unique-key用来接收主键，data-my-unique-property用来接受email这个值。
Directive部分大致如下：
(function(){var injectParams = ['$q', 'dataService'];var myUniqueDirective = function($q, dataService){var link = function(scope, element, attrs, ngModel){ngModel.$asyncValidators.unique = function(modelValue, viewValue){var deferred = $q.defer(),currentValue = modelValue || viewValue,//获取主键key = attrs.myUniqueKey,//my-unqiue-key = "{{customer.id}}"//获取emailproperty=attrs.myUnqiueProperty; //my-unique-property="email"if(key && property){dataService.checkUniqueValue(key, property, currentValue).then(function(unique){if(unique){deferred.resolve();} else {deferred.reject();}});return deferred.promise;} else {return $q.when(true);}}};return {restrict: 'A',require: 'ngModel',link: link}};myUniqueDirective.$inject = injectParams;angular.module('customersApp').directive('myUnique', myUniqueDirective); }());