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Using Injector within a Service in Angular

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by Abdul Rawoof A R dot icon Updated: Jan 5, 2024

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To retrieve object instances defined by the provider, instantiate types, invoke methods, and load modules injector is used. It defines a class as a service in Angular and will allow Angular to inject it into a component as a dependency. 


The @Injectable decorator is optional if you use the 'providedIn' option. The @Injectable decorator and the 'providedIn' option is the service that should not be added within the providers' array of a module. The main difference between the injector and injectable is that we use the @Inject parameter decorator to instruct Angular that we want to fix a token and inject a dependency into a constructor. We use the @Injectable class decorators to automatically improve and inject all the class constructor parameters. 

  • Constructor injection: it provides the dependencies through a class constructor. 
  • Setter injection: The client will use a setter method into which the injector injects the dependency.


Here is an example of how to use an injector within a service in Angular:

Fig: Preview of the output that you will get on running this code from your IDE.

Code

Error when using angular.injector() within a service

Lines of Code : 53dotLicense : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries : 
<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.3.x" src="https://code.angularjs.org/1.3.20/angular.js" data-semver="1.3.20"></script>

    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <p>Hello {{name}}!</p>
  </body>

</html>

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

app.controller('MainCtrl', function($scope) {
  $scope.name = 'World';


  var $injector = angular.injector(['ng', 'plunker']);
  var a = $injector.get('myService')
  console.log(a);
});

app.factory('pseudoService', pseudoService);

var pseudoService = function(){
    var service = myService;
    myService.sayHello();
    return{
     service:service
    }
}



var myService = function(){
  var sayHello = function(){
    alert("Hello")
  }
  return{
    sayHello:sayHello
  }
}

app.service('myService', myService);

Instructions

Follow the steps carefully to get the output easily.

  1. Install Visual Studio Code on your computer.
  2. Create a folder in your local.
  3. Then open that folder from File->Open Folder.
  4. Create a js file(eg: app.js).
  5. Create a HTML file(eg: index.html).
  6. Copy the HTML code from snippet and paste it into that HTML file.
  7. Then copy the balance code and paste it into that app.js file.
  8. Save and run the file directly from the file location to get the output.


I hope you found this helpful.


I found this code snippet by searching for 'using angular injector within a service' in kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created and tested in Visual Studio Code 1.74.1.


Using this solution, we are able to use injector within a service in Angular with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to use injector within a service in Angular.

FAQ

1. What is an Injector in Angular?

Angular is an Injector is a dependency injection container responsible for creating instances. It is part of Angular's dependency injection system. It provides a way to manage and inject dependencies into component services.


2. How can an Injector be used within a service in Angular?

A service in Angular can use an Injector to get instances of other services or dependencies. This can be done by injecting the Injector into the service's constructor and then using it.


3. Why would a service use an Injector to get dependencies?

The Injector within a service allows for dynamic retrieval of dependencies. This can be useful in scenarios where the service needs to interact with dependencies. It provides flexibility in managing dependencies within the service.


4. How does the Injector resolve dependencies?

The Injector in Angular resolves dependencies by traversing the hierarchical tree of injectors. When a service requests a dependency, the Injector checks if it has the dependency. If not, it delegates the request to its parent injector. This process continues until the root injector is reached or the dependency is found.


5. Can an Injector be used outside of Angular services and components?

Yes, an Injector can be used outside of Angular services and components. It can create a standalone Injector Create () and use it in non-Angular contexts. It is within regular TypeScript code or in libraries that are not Angular-specific.


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