What is the best method for invoking ajax requests from a service in AngularJS?

I am working on an Employee controller that includes properties such as Id, Name, and Specification. I have created an Employee service which makes an ajax call to retrieve a list of employees. However, every time I make the call, I receive an empty response in the User field. Upon debugging the code, I discovered that the success function is called first before the actual ajax call is made. Interestingly, when I make the ajax call without using the service, everything works as expected.

 angular.module('EmployeeServiceModule', [])
.service('EmployeeSer', ['$http',function ($http) {
    this.Users = '';
    this.errors = '';
    this.SearchEmployee = function () {
 // Ajax call
        $http({
            method: 'GET',
            url: '/Home/GetEmployeeList',
            params: { filterData: 'Test' },
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
        }).then(onSuccess, onError);

        var onSuccess = function (response) {
            this.userUsers = response.data;
            this.errors = '';
        };

        var onError = function (reason) {
            this.userUsers = reason;
            this.errors = "Error in retrieving data.";
        };

        return this.Users;
    }   
}]);


angular.module('Employee', ['EmployeeServiceModule'])
.controller('EmployeeController', ['EmployeeSer', '$scope', '$http', function (EmployeeSer, $scope, $http) {

    this.Id = '';
    this.name = '';
    this.expertise = '';
    $scope.repoSortOrder = 'id';
    $scope.filterField = '';

    // Call to service
    this.GetAllEmployee = function () {
        // Initiates the AJAX call
        $scope.User = EmployeeSer.SearchEmployee();
        // Returns the promise - Contains result once request completes
        return true;
    };

    this.AddEmployee = function () {
        var empData = {
            Id: $("#txtId").val(),
            Name: $("#txtName").val(),
            Expertise: $("#expertise").val()
        };

        $http({
            method: 'POST',
            url: '/Home/Create',
            params: JSON.stringify(empData),
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
        }).then(onSuccess, onError);
        // Returns the promise - Contains result once request completes
        return true;
    };

    var onSuccess = function (response) {
        $scope.user = response.data;
        $scope.error = '';
    };

    var onError = function (reason) {
        $scope.error = "Error in retrieving data.";
    };

}]);

Answer №1

It appears that the issue arises from returning user data before it is retrieved from the server and potential incorrect assignment methods.

To address this problem, there are two possible solutions:

Firstly, establish a binding between the user-data in your controller and the service's user-data.

angular.module('EmployeeServiceModule', [])
      .service('EmployeeSer', ['$http',function ($http) {
          this.Users = '';
          this.errors = '';
          $http({
             method: 'GET',
             url: '/Home/GetEmployeeList',
             params: { filterData: 'Test' },
             headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
          }).then(onSuccess, onError);

          var onSuccess = function (response) {
              this.Users = response.data;
              this.errors = '';
          };

         var onError = function (reason) {
              this.users = null;
              this.errors = "Error in retrieving data.";
         };
     }   
}]);


angular.module('Employee', ['EmployeeServiceModule'])
       .controller('EmployeeController', ['EmployeeSer', '$scope', '$http', function (EmployeeSer, $scope, $http) {
           this.users = EmployeeSer.users;
           EmployeeSer.SearchEmployee();
}]);

The second approach involves returning a promise from the service and handling it within the controller.

angular.module('EmployeeServiceModule', [])
       .service('EmployeeSer', ['$http',function ($http) {
          this.SearchEmployee = function () {
               return $http({
                  method: 'GET',
                  url: '/Home/GetEmployeeList',
                  params: { filterData: 'Test' },
                  headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
               });
          }   
}]);


angular.module('Employee', ['EmployeeServiceModule'])
       .controller('EmployeeController', ['EmployeeSer', '$scope', $http', function (EmployeeSer, $scope, $http) {

       this.GetAllEmployee = function () {
            EmployeeSer.SearchEmployee()
                       .then(onSuccess, onError)
       };

       var onSuccess = function (response) {
            $scope.user = response.data;
            $scope.error = '';
       };

       var onError = function (reason) {
            $scope.error = "Error in retrieving data.";
       };

}]);

SIDE NOTE Consider utilizing ngModel instead of jQuery for obtaining data in your controller. Avoid using this technique:

var empData = {
      Id: $("#txtId").val(),
      Name: $("#txtName").val(),
      Expertise: $("#expertise").val()
};

Answer №2

// Introducing the serverRequest service for making server requests

serverRequest.postReq = function(url, data, successCallback, errorCallback){
$http({
method: 'POST', 
url: urlToBeUsed, 
data:data,
headers : {'Content-Type': 'application/x-www-form-urlencoded'}})
.success(function(data, status, headers, config) {
successCallback(data);
})
.error(function(data, status, headers, config){
errorCallback(data);
})
}

// Usage in the controller
serverRequest.postReq('urlToBeCalled', dataToBeSent, scope.successCb, scope.errorCb);

scope.successCb = function(data){
// Add your functionality here
}
scope.errorCb = function(data){
// Add your functionality here
}

Give this approach a try to potentially resolve your issue
Remember to unwrap the Promise in your controller if you intend to utilize it

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