How to manage and use dependencies in AngularJS modules?
13/03/2024
•
5
min
To manage and use dependencies effectively in AngularJS modules, follow the below step-by-step guidelines. For example, let's create an AngularJS service that depends on $http to make AJAX calls.
Step 1: Creating the main module
The first step is to create the main module. In your HTML page, you can include the AngularJS reference and create a new AngularJS app (module). The first parameter of the angular.module function is the name of the app/module, and the second argument is an array of dependencies. In this case, the mainApp module has no dependencies, therefore, the array is empty.
<!doctype html>
<html lang="en" ng-app="mainApp">
<head>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js"></script>
<script src="main.js"></script>
</head>
<body>
<div ng-controller="helloController">...</div>
</body>
</html>
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Step 2: Defining the service
Next, let's define a service named 'HelloService'. This service depends on the $http service to make AJAX requests. To define a service, we use the factory method on an AngularJS module. The first parameter of the factory function is the name of the service and the second parameter is a function that defines the service.
This function takes as arguments the dependencies of the service. In this case, our service depends on $http. The function returns an object with the functionality of the service. In our case, the service exposes a single function named sayHello that makes an AJAX request to a URL and returns the resulting promise.
angular.module('mainApp').factory('HelloService', function($http) {
return {
sayHello: function() {
return $http({
method: 'GET',
url: 'some/url'
});
}
};
});
Step 3: Defining a controller that depends on the service
Now, let's define a controller named 'helloController'. The controller depends on two services: the $scope and our HelloService.
We create the controller using the controller method on an AngularJS module. The first parameter is the name of the controller and the second parameter is the constructor function for the controller. The function takes as arguments the dependencies of the controller.
Within the controller, we can now assign the result of the HelloService's sayHello function to a variable in the $scope. We assign it to $scope.greeting.
angular.module('mainApp').controller('helloController', function($scope, HelloService) {
HelloService.sayHello().then(function(response) {
$scope.greeting = response.data;
});
});
The AngularJS $injector service is responsible for creating components, resolving their dependencies, and providing them to other components as requested.
One more important logic Angular uses is Dependency Annotation. This is the way to provide the metadata information of dependencies to Angular. AngularJS provides three ways to add dependency annotation with components: Inline Array Annotation, $inject Property Annotation and Implicit Annotation. But the recommended way is Inline Array Annotation as it's minification safe.
AngularJS handles all the tasks related to dependency injection internally itself and provides a clean interface to work with there components effectively. You just need to specify what you need and AngularJS takes care of creating and injecting it to where you need it.
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