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Sunday, February 12, 2017

AngularJS - Services

AngularJS supports the concepts of "Separation of Concerns" using services architecture. Services are javascript functions and are responsible to do a specific tasks only. This makes them an individual entity which is maintainable and testable.
Controllers, filters can call them as on requirement basis. Services are normally injected using dependency injection mechanism of AngularJS.
AngularJS provides many inbuilt services for example, $https:, $route, $window, $location etc. Each service is responsible for a specific task for example, $https: is used to make ajax call to get the server data. $route is used to define the routing information and so on. Inbuilt services are always prefixed with $ symbol.
There are two ways to create a service.
  • factory
  • service

Using factory method

Using factory method, we first define a factory and then assign method to it.
var mainApp = angular.module("mainApp", []);
mainApp.factory('MathService', function() {
   var factory = {};
   
   factory.multiply = function(a, b) {
      return a * b
   }
   
   return factory;
});

Using service method

Using service method, we define a service and then assign method to it. We've also injected an already available service to it.
mainApp.service('CalcService', function(MathService){
   this.square = function(a) {
      return MathService.multiply(a,a);
   }
});

Example

Following example will showcase all the above mentioned directives.
testAngularJS.htm
<html>

   <head>
      <title>Angular JS Services</title>
      <script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
   </head>
   
   <body>
      <h2>AngularJS Sample Application</h2>
      
      <div ng-app = "mainApp" ng-controller = "CalcController">
         <p>Enter a number: <input type = "number" ng-model = "number" /></p>
         <button ng-click = "square()">X<sup>2</sup></button>
         <p>Result: {{result}}</p>
      </div>
      
      <script>
         var mainApp = angular.module("mainApp", []);
         
         mainApp.factory('MathService', function() {
            var factory = {};
            
            factory.multiply = function(a, b) {
               return a * b
            }
            return factory;
         });
         
         mainApp.service('CalcService', function(MathService){
            this.square = function(a) {
               return MathService.multiply(a,a);
            }
         });
         
         mainApp.controller('CalcController', function($scope, CalcService) {
            $scope.square = function() {
               $scope.result = CalcService.square($scope.number);
            }
         });
      </script>
      
   </body>
</html>

Result

Open textAngularJS.htm in a web browser. See the result.
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