如何在AngularJS中正确使用HTTP.GET?具体而言，对于外部API调用

首先，success()处理程序只返回数据，但不会返回给getData()的调用者，因为它已经在回调中了。$http是一个异步调用，它返回一个$promise，因此您必须为数据可用时注册一个回调。

我建议在AngularJS中查找Promises和$q库，因为它们是在服务之间传递异步调用的最佳方式。

为了简单起见，下面是用调用控制器提供的函数回调重新编写的相同代码：

var myApp = angular.module('myApp',[]);
myApp.service('dataService', function($http) {
    delete $http.defaults.headers.common['X-Requested-With'];
    this.getData = function(callbackFunc) {
        $http({
            method: 'GET',
            url: 'https://www.example.com/api/v1/page',
            params: 'limit=10, sort_by=created:desc',
            headers: {'Authorization': 'Token token=xxxxYYYYZzzz'}
        }).success(function(data){
            // With the data succesfully returned, call our callback
            callbackFunc(data);
        }).error(function(){
            alert("error");
        });
     }
});
myApp.controller('AngularJSCtrl', function($scope, dataService) {
    $scope.data = null;
    dataService.getData(function(dataResponse) {
        $scope.data = dataResponse;
    });
});

现在，$http实际上已经返回了$promise，所以这可以重写：

var myApp = angular.module('myApp',[]);
myApp.service('dataService', function($http) {
    delete $http.defaults.headers.common['X-Requested-With'];
    this.getData = function() {
        // $http() returns a $promise that we can add handlers with .then()
        return $http({
            method: 'GET',
            url: 'https://www.example.com/api/v1/page',
            params: 'limit=10, sort_by=created:desc',
            headers: {'Authorization': 'Token token=xxxxYYYYZzzz'}
         });
     }
});
myApp.controller('AngularJSCtrl', function($scope, dataService) {
    $scope.data = null;
    dataService.getData().then(function(dataResponse) {
        $scope.data = dataResponse;
    });
});

最后，还有更好的方法来配置$http服务，以便使用config()设置$httpProvider来处理标头。查看$http文档中的示例。

我建议您使用Promise

myApp.service('dataService', function($http,$q) {
  delete $http.defaults.headers.common['X-Requested-With'];
  this.getData = function() {
     deferred = $q.defer();
     $http({
         method: 'GET',
         url: 'https://www.example.com/api/v1/page',
         params: 'limit=10, sort_by=created:desc',
         headers: {'Authorization': 'Token token=xxxxYYYYZzzz'}
     }).success(function(data){
         // With the data succesfully returned, we can resolve promise and we can access it in controller
         deferred.resolve();
     }).error(function(){
          alert("error");
          //let the function caller know the error
          deferred.reject(error);
     });
     return deferred.promise;
  }
});

因此，在您的控制器中，您可以使用方法

myApp.controller('AngularJSCtrl', function($scope, dataService) {
    $scope.data = null;
    dataService.getData().then(function(response) {
        $scope.data = response;
    });
});

promise是angularjs的强大功能，如果您想避免嵌套回调，它非常方便。

无需承诺$http，我只使用两个返回：

 myApp.service('dataService', function($http) {
   this.getData = function() {
      return $http({
          method: 'GET',
          url: 'https://www.example.com/api/v1/page',
          params: 'limit=10, sort_by=created:desc',
          headers: {'Authorization': 'Token token=xxxxYYYYZzzz'}
      }).success(function(data){
        return data;
      }).error(function(){
         alert("error");
         return null ;
      });
   }
 });

控制器内

 myApp.controller('AngularJSCtrl', function($scope, dataService) {
     $scope.data = null;
     dataService.getData().then(function(response) {
         $scope.data = response;
     });
 }); 

试试这个

myApp.config(['$httpProvider', function($httpProvider) {
        $httpProvider.defaults.useXDomain = true;
        delete $httpProvider.defaults.headers.common['X-Requested-With'];
    }
]);

仅仅设置useXDomain=true是不够的。AJAX请求也使用X-Requested-WithHeader发送，这表明它们是AJAX。删除标头是必要的，这样服务器就不会拒绝传入的请求。

所以您需要使用我们所说的promise。在这里阅读angular是如何处理的，https://docs.angularjs.org/api/ng/service/$q。将我们的$http支持承诺转化为内在的，因此在您的情况下，我们将这样做，

(function() {
  "use strict";
  var serviceCallJson = function($http) {
      this.getCustomers = function() {
        // http method anyways returns promise so you can catch it in calling function
        return $http({
            method : 'get',
            url : '../viewersData/userPwdPair.json'
          });
      }
  }
  var validateIn = function (serviceCallJson, $q) {
      this.called = function(username, password) {
          var deferred = $q.defer(); 
          serviceCallJson.getCustomers().then( 
            function( returnedData ) {
              console.log(returnedData); // you should get output here this is a success handler
              var i = 0;
              angular.forEach(returnedData, function(value, key){
                while (i < 10) {
                  if(value[i].username == username) {
                    if(value[i].password == password) {
                     alert("Logged In");
                    }
                  }
                  i = i + 1;
                }
              });
            }, 
            function() {
              // this is error handler
            } 
          );
          return deferred.promise;  
      }
  }
  angular.module('assignment1App')
    .service ('serviceCallJson', serviceCallJson)
  angular.module('assignment1App')
  .service ('validateIn', ['serviceCallJson', validateIn])
}())

以谷歌金融为例检索股票行情的最后收盘价和更新日期&时间您可以访问YouTiming.com进行运行时执行。

服务：

MyApp.service('getData', 
  [
    '$http',
    function($http) {
      this.getQuote = function(ticker) {
        var _url = 'https://www.google.com/finance/info?q=' + ticker;
        return $http.get(_url); //Simply return the promise to the caller
      };
    }
  ]
);

控制器：

MyApp.controller('StockREST', 
  [
    '$scope',
    'getData', //<-- the service above
    function($scope, getData) {
      var getQuote = function(symbol) {
        getData.getQuote(symbol)
        .success(function(response, status, headers, config) {
          var _data = response.substring(4, response.length);
          var _json = JSON.parse(_data);
          $scope.stockQuoteData = _json[0];
          // ticker: $scope.stockQuoteData.t
          // last price: $scope.stockQuoteData.l
          // last updated time: $scope.stockQuoteData.ltt, such as "7:59PM EDT"
          // last updated date & time: $scope.stockQuoteData.lt, such as "Sep 29, 7:59PM EDT"
        })
        .error(function(response, status, headers, config) {
          console.log('@@@ Error: in retrieving Google Finance stock quote, ticker = ' + symbol);
        });
      };
      getQuote($scope.ticker.tick.name); //Initialize
      $scope.getQuote = getQuote; //as defined above
    }
  ]
);

HTML：

<span>{{stockQuoteData.l}}, {{stockQuoteData.lt}}</span>

在YouTiming.com主页的顶部，我放置了关于如何在Chrome和Safari上禁用CORS策略的说明。

当调用在服务或工厂中定义的promise时，请确保使用服务，因为我无法从工厂中的promise获得响应。这就是我对服务中定义的承诺的调用方式。

myApp.service('serverOperations', function($http) {
        this.get_data = function(user) {
          return $http.post('http://localhost/serverOperations.php?action=get_data', user);
        };
})

myApp.controller('loginCtrl', function($http, $q, serverOperations, user) {        
    serverOperations.get_data(user)
        .then( function(response) {
            console.log(response.data);
            }
        );
})