Angular Dependency Injection – Understanding Hierarchical Injectors

Dependency Injection in Angular is a big and hard topic but it is crucial to understand it at least on some basic level in order to build scalable, testable and flexible components and applications. Why do we need DI in Angular? What happens behind the scenes? How Angular resolves dependencies? Answers on all this questions you will find in this video tutorial.

🕒 Time codes:
00:00:00 - Intro
00:01:00 - Why do we need Dependency Injection?
00:03:00 - Let’s create our own DI prototype
00:08:49 - Hierarchical Dependency Injection in Angular explained
00:12:17 - Dependency resolution rules
00:15:43 - Outro

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Angular Dependency Injection – Understanding Hierarchical Injectors
Christa  Stehr

Christa Stehr


Install Angular - Angular Environment Setup Process

Angular is a TypeScript based framework that works in synchronization with HTML, CSS, and JavaScript. To work with angular, domain knowledge of these 3 is required.

  1. Installing Node.js and npm
  2. Installing Angular CLI
  3. Creating workspace
  4. Deploying your First App

In this article, you will get to know about the Angular Environment setup process. After reading this article, you will be able to install, setup, create, and launch your own application in Angular. So let’s start!!!

Angular environment setup

Install Angular in Easy Steps

For Installing Angular on your Machine, there are 2 prerequisites:

  • Node.js
  • npm Package Manager

First you need to have Node.js installed as Angular require current, active LTS or maintenance LTS version of Node.js

Download and Install Node.js version suitable for your machine’s operating system.

Npm Package Manager

Angular, Angular CLI and Angular applications are dependent on npm packages. By installing Node.js, you have automatically installed the npm Package manager which will be the base for installing angular in your system. To check the presence of npm client and Angular version check of npm client, run this command:

  1. npm -v

Installing Angular CLI

  • Open Terminal/Command Prompt
  • To install Angular CLI, run the below command:
  1. npm install -g @angular/cli

installing angular CLI

· After executing the command, Angular CLI will get installed within some time. You can check it using the following command

  1. ng --version

Workspace Creation

Now as your Angular CLI is installed, you need to create a workspace to work upon your application. Methods for it are:

  • Using CLI
  • Using Visual Studio Code
1. Using CLI

To create a workspace:

  • Navigate to the desired directory where you want to create your workspace using cd command in the Terminal/Command prompt
  • Then in the directory write this command on your terminal and provide the name of the app which you want to create. In my case I have mentioned DataFlair:
  1. Ng new YourAppName

create angular workspace

  • After running this command, it will prompt you to select from various options about the CSS and other functionalities.

angular CSS options

  • To leave everything to default, simply press the Enter or the Return key.

angular setup

#angular tutorials #angular cli install #angular environment setup #angular version check #download angular #install angular #install angular cli

Lilyan  Streich

Lilyan Streich


Angular 9 Dependency Injection Example Tutorial

Dependencies are services or objects that a class needs to perform its function. DI is a coding pattern in which a class asks for dependencies from external sources rather than creating them itself.

In Angular, the DI framework provides declared dependencies to a class when that class is instantiated. This guide explains how DI works in Angular, and how you use it to make your apps flexible, efficient, and robust, as well as testable and maintainable.

Angular Dependency injection is an essential application design pattern. Angular has its dependency injection framework, and you really can’t build an Angular application without it. It’s used so widely that almost everyone just calls it DI.

#angular #angular 9 #angular dependency injection

Roberta  Ward

Roberta Ward


Basics of Angular: Part-1

What is Angular? What it does? How we implement it in a project? So, here are some basics of angular to let you learn more about angular.

Angular is a Typescript-based open-source front-end web application platform. The Angular Team at Google and a community of individuals and corporations lead it. Angular lets you extend HTML’s syntax to express your apps’ components clearly. The angular resolves challenges while developing a single page and cross-platform applications. So, here the meaning of the single-page applications in angular is that the index.html file serves the app. And, the index.html file links other files to it.

We build angular applications with basic concepts which are NgModules. It provides a compilation context for components. At the beginning of an angular project, the command-line interface provides a built-in component which is the root component. But, NgModule can add a number of additional components. These can be created through a template or loaded from a router. This is what a compilation context about.

What is a Component in Angular?

Components are key features in Angular. It controls a patch of the screen called a view. A couple of components that we create on our own helps to build a whole application. In the end, the root component or the app component holds our entire application. The component has its business logic that it does to support the view inside the class. The class interacts with the view through an API of properties and methods. All the components added by us in the application are not linked to the index.html. But, they link to the app.component.html through the selectors. A component can be a component and not only a typescript class by adding a decorator @Component. Then, for further access, a class can import it. The decorator contains some metadata like selector, template, and style. Here’s an example of how a component decorator looks like:

    selector: 'app-root',
    templateUrl: 'app.component.html',
    styleUrls: ['app.component.scss']

Role of App Module

Modules are the package of functionalities of our app. It gives Angular the information about which features does my app has and what feature it uses. It is an empty Typescript class, but we transform it by adding a decorator @NgModule. So, we have four properties that we set up on the object pass to @NgModule. The four properties are declarations, imports, providers, and bootstrap. All the built-in new components add up to the declarations array in @NgModule.

declarations: [
imports: [
bootstrap: [AppComponent]

What is Data Binding?

Data Binding is the communication between the Typescript code of the component and the template. So, we have different kinds of data binding given below:

  • When there is a requirement to output data from our Typescript code in the HTML template. String interpolation handles this purpose like {{data}} in HTML file. Property Binding is also used for this purpose like [property] = “data”.
  • When we want to trigger any event like clicking a button. Event Binding works while we react to user events like (event) = “expression”.
  • When we can react to user events and output something at the same time. Two-way Binding is used like [(ngModel)] = “data”.

image for understanding data binding

#angular #javascript #tech blogs #user interface (ui) #angular #angular fundamentals #angular tutorial #basics of angular

Sasha  Roberts

Sasha Roberts


Dependency Injection In Angular

In this video, we will see how the Dependency Injection (#DI) works in #angular. We will also see the Inversion Of Control (#IoC) principle, and the Dependency Inversion Principle (#DIP).

The Dependency Injection is a design pattern under the umbrella of the Inversion Of Control principle.

In the Angular Providers, when we use #useClass, Angular will try to create a new class instance.
When we use #useExisting, we tell Angular to use an existing class instance.

In this example, the correct approach is to use #useExisting since the loggers are singleton and we don’t need to create a new instance.


#angular #angular tutorial #what is angular

Arvel  Parker

Arvel Parker


Inject Objects Into Your Component with Angular Dependency Injection

Dependency Injection is a common design pattern to deal with dependencies. Instead of creating instances of dependencies yourself when you need them, you leave this task to a dependency injection mechanism. This mechanism instantiates the dependencies when needed and gives you access to these instances, in order to avoid having to create and deal with too many instances of the same thing.
Angular, as the complete JavaScript framework it is, comes with its own dependency injection mechanism. Most of the time, the dependencies we are talking about are services. To learn more about how to inject services you can check this article. But dependency injection is not limited to services. You can use it to inject (almost) anything you like, for example objects. However, while a syntax shortcut makes injecting a service pretty straight-forward, there is a bit more work when injecting other types of objects.

#dependency-injection #javascript #web-development #angular