How to instantiate a service dynamically? - angularjs

Question

I have a Utils Service which is very heavy. I Want to use some of the functions defined in it on a particular user action. As this service is heavy I want to instantiate it lazily(on user action).
How do I achieve this?
Service
module.service('Utils', function (dep1, dep2) {
this.method1 = function () {
// do something
}
// other methods
});
Controller
module.controller('AppCtrl', function ($scope) {
// I don't want to inject Utils as a dependency.
$scope.processUserAction = function () {
// If the service is not instantiated
// instantiate it and trigger the methods defined in it.
}
});
Markup
<div data-ng-controller="AppCtrl">
<button data-ng-click="processUserAction()"> Click Me </button>
</div>

Answer 1

You can use $injector service to get services anywhere: https://docs.angularjs.org/api/auto/service/$injector. Inject the $injector into your controller, and whenever you need a service use:
This worked fine for me, the service is instantiated only on the $injector call, no error thrown.
angular.module('yp.admin')
.config(['$stateProvider', '$urlRouterProvider', 'accessLevels', '$translateWtiPartialLoaderProvider',
function ($stateProvider, $urlRouterProvider, accessLevels, $translateWtiPartialLoaderProvider) {
$stateProvider
.state('admin.home', {
url: "/home",
access: accessLevels.admin,
views: {
content: {
templateUrl: 'admin/home/home.html',
controller: 'AdminHomeController'
}
}
});
}])
.service('UtilsService', function() {
console.log('utilsSerivce instantiated');
return {
call: function() {
console.log('Util.call called');
}
};
})
.controller('AdminHomeController', ['$scope', '$rootScope', 'UserService', '$injector',
function($scope, $rootScope, UserService, $injector) {
$injector.get('UtilsService').call();
}]);
console gives me this:
stateChangeStart from: to: admin.home
stateChangeSuccess from: to: admin.home
utilsSerivce instantiated
Util.call called
If you want to delay loading the JS you should have a look at the ocLazyLoad Module: https://github.com/ocombe/ocLazyLoad. It addresses all sorts of lazy loading use cases and yours sounds like a good fit for it.