How to use HTTP.GET in AngularJS correctly? In specific, for an external API call?

Question

I have the following code in the controller.js,

var myApp = angular.module('myApp',[]);

myApp.service('dataService', function($http) {
delete $http.defaults.headers.common['X-Requested-With'];
this.getData = function() {
    $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");
    });
 }
});

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

But, I think I m probably making a mistake with CORS related issue. Can you please point me to the correct way to make this call? Thanks much!

Answer 1

First, your success() handler just returns the data, but that's not returned to the caller of getData() since it's already in a callback. $http is an asynchronous call that returns a $promise, so you have to register a callback for when the data is available.

I'd recommend looking up Promises and the $q library in AngularJS since they're the best way to pass around asynchronous calls between services.

For simplicity, here's your same code re-written with a function callback provided by the calling controller:

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;
    });
});

Now, $http actually already returns a $promise, so this can be re-written:

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;
    });
});

Finally, there's better ways to configure the $http service to handle the headers for you using config() to setup the $httpProvider. Checkout the $http documentation for examples.

Answer 2

I suggest you use 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;
  }
});

so In your controller you can use the method

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

promises are powerful feature of angularjs and it is convenient special if you want to avoid nesting callbacks.

Answer 3

No need to promise with $http, i use it just with two returns :

 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 ;
      });
   }
 });

In controller

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

Answer 4

Try this

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

Just setting useXDomain = true is not enough. AJAX request are also send with the X-Requested-With header, which indicate them as being AJAX. Removing the header is necessary, so the server is not rejecting the incoming request.

Answer 5

So you need to use what we call promise. Read how angular handles it here, https://docs.angularjs.org/api/ng/service/$q. Turns our $http support promises inherently so in your case we'll do something like this,

(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])

}())

Answer 6

Using Google Finance as an example to retrieve the ticker's last close price and the updated date & time. You may visit YouTiming.com for the run-time execution.

The service:

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
      };
    }
  ]
);

The controller:

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
    }
  ]
);

The HTML:

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

At the top of YouTiming.com home page, I have placed the notes for how to disable the CORS policy on Chrome and Safari.