部分场景下,我们希望在拦截器中能够执行一些异步操作.然后依据不同的处理结果进行不同的拦截操作,AngularJS在设计的时候也很好的支持了这一特性.AngularJS允许我们在拦截的方法中,我们可以返回一个promise对象.如在http服务中,我们如果返回一个promise对象时,http服务将会延迟发起网络请求或是延迟响应请求结果.
module.factory('myInterceptor', ['$q', 'someAsyncService', function($q, someAsyncService) { var requestInterceptor = { request: function(config) { var deferred = $q.defer(); someAsyncService.doAsyncOperation().then(function() { // Asynchronous operation succeeded, modify config accordingly ... deferred.resolve(config); }, function() { // Asynchronous operation failed, modify config accordingly ... deferred.resolve(config); }); return deferred.promise; }, response: function(response) { var deferred = $q.defer(); someAsyncService.doAsyncOperation().then(function() { // Asynchronous operation succeeded, modify response accordingly ... deferred.resolve(response); }, function() { // Asynchronous operation failed, modify response accordingly ... deferred.resolve(response); }); return deferred.promise; } }; return requestInterceptor; }]);
上面的例子中,在请求发起时,如果对应的deferred被拒绝，http请求则会失败(如果进行抓包分析的话,你会发现http请求并没有发起).在请求进行响应时,如果deferred被拒绝,则请求也会失败.(抓包分析,网络请求是有返回的).