AngularJS中的promise用法分析

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2017-05-19

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本文实例讲述了AngularJS中的promise用法。分享给大家供大家参考，具体如下：

JavaScript异步回调有好处也有坏处，回调函数大量嵌套十分复杂．所以javascript中还有另一种异步处理模式叫promises．在AngularJS中的实现就是$q服务．

下面是一些小例子．

then,catch,finally

在链最后的 catch 为整个链式处理提供一个异常处理点
在链最后的 finally 总是会被执行，不管 promise 被处理或者被拒绝，起清理作用

<!DOCTYPE html>
<html>
  <head>
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
    <script src="jQuery.min.js"></script>
    <script src="angular.min.js"></script>
    <script src="bootstrap.min.js"></script>
    <script type="text/javascript">
      var myapp = angular.module('myapp', []);
      myapp.controller('myController', function($scope, $q) {
        $scope.send = function() {
          var deferred = $q.defer();
          var promise = deferred.promise;
          promise
          .then(function() {
            console.log('resolve.....')
          }, function() {
            console.log('reject.....');
          }, function() {
            console.log('notify.....');
          })
          .catch(function() {
            console.log('catch..error..')
          })
          .finally(function() {
            console.log('anywhere will be called..');
          });
          deferred.reject('resolve');
        };
      });
    </script>
    <style type="text/css">
    </style>
  </head>
  <body ng-app="myapp">
    <div ng-controller="myController">
        <button class="btn" ng-click="send()">click</button>
    </div>
  </body>
</html>

then第三个参数(表征状态)的应用

<!DOCTYPE html>
<html>
  <head>
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
    <script src="jquery.min.js"></script>
    <script src="angular.min.js"></script>
    <script src="bootstrap.min.js"></script>
    <script type="text/javascript">
      var myapp = angular.module('myapp', []);
      myapp.controller('myController', function($scope, dataService) {
        $scope.send = function() {
          dataService.getData()
          .then(function success(data) {
            console.log(data);
          }, function error(error) {
            console.log(error);
          }, function status(process) {
            console.log(process);
          });
        };
      });
      myapp.factory('dataService', function($q, $interval) {
        return {
          getData : function() {
            var deferred = $q.defer();
            var process = 0;
            var interval = $interval(function() {
              process += 10;
              deferred.notify(process);
              //reject之后不再继续运行
              // if (process == 50) {
              //   deferred.reject(process);
              // }
              if (process >= 100) {
                $interval.cancel(interval);
                deferred.resolve(process);
              }
            }, 1000);
            return deferred.promise;
          }
        };
      });
    </script>
    <style type="text/css">
    </style>
  </head>
  <body ng-app="myapp">
    <div ng-controller="myController">
        <button class="btn" ng-click="send()">click</button>
    </div>
  </body>
</html>

then链式

<!DOCTYPE html>
<html>
  <head>
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
    <script src="jquery.min.js"></script>
    <script src="angular.min.js"></script>
    <script src="bootstrap.min.js"></script>
    <script type="text/javascript">
      var myapp = angular.module('myapp', []);
      myapp.controller('myController', function($scope, $q) {
        $scope.send = function() {
          var deferred = $q.defer();
          var promise = deferred.promise;
          promise
          .then(function() {
            console.log('1.....')
          })
          .then(function() {
            console.log('2....');
          });
          deferred.resolve('resolve');
        };
      });
    </script>
    <style type="text/css">
    </style>
  </head>
  <body ng-app="myapp">
    <div ng-controller="myController">
        <button class="btn" ng-click="send()">click</button>
    </div>
  </body>
</html>

then链会把上一个 then 的返回结果传递给调用链的下一个 then (如果没有就是 undefined).

<!DOCTYPE html>
<html>
  <head>
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="bootstrap.min.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
    <script src="jquery.min.js"></script>
    <script src="angular.min.js"></script>
    <script src="bootstrap.min.js"></script>
    <script type="text/javascript">
      var myapp = angular.module('myapp', []);
      myapp.controller('myController', function($scope, $q, $timeout) {
        $scope.send = function() {
          var deferred = $q.defer();
          var promise = deferred.promise;
          deferred.resolve('resolve');
          promise
          .then(function(data) {
            console.log(data);
            var _deferred = $q.defer();
            $timeout(function() {
            _deferred.resolve('resolve_');
            }, 1000);
            return _deferred.promise;
          })
          .then(function(data) {
            console.log(data);
          });
        };
      });
    </script>
    <style type="text/css">
    </style>
  </head>
  <body ng-app="myapp">
    <div ng-controller="myController">
        <button class="btn" ng-click="send()">click</button>
    </div>
  </body>
</html>

如果 then 返回一个 promise 对象，下一个 then 只会在这个 promise 被处理结束的时候调用。

更多关于AngularJS相关内容感兴趣的读者可查看本站专题：《AngularJS指令操作技巧总结》、《AngularJS入门与进阶教程》及《AngularJS MVC架构总结》

希望本文所述对大家AngularJS程序设计有所帮助。

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