Injecting services into components in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of injecting a service into an Angular component?

Injecting a service allows the component to use shared logic or data provided by the service, promoting code reuse and separation of concerns.

intermediate

How do you inject a service into a standalone Angular component?

Use the inject() function inside the component's code to get the service instance, instead of constructor injection.

beginner

What decorator is used to make a class a service that can be injected?

The <code>@Injectable()</code> decorator marks a class as a service that Angular can inject into components or other services.

intermediate

What is the difference between injecting a service via constructor and using the inject() function?

Constructor injection is the traditional way and works in class-based components, while inject() is a new function useful in standalone components and functional contexts.

beginner

Why is dependency injection important in Angular applications?

It helps manage dependencies cleanly, makes testing easier, and allows components to stay focused on UI logic without managing service creation.

Which Angular decorator is used to define a service that can be injected?

A @Injectable

B @Component

C @NgModule

D @Directive

The @Injectable decorator marks a class as a service that Angular can inject.

In Angular 17+, what function can be used inside a standalone component to inject a service?

A inject()

B useService()

C getService()

D provide()

The inject() function is the new recommended way to inject services in standalone components.

What is the main benefit of injecting services into components?

A Avoid using Angular modules

B Make components heavier

C Reuse logic and separate concerns

D Directly manipulate the DOM

Injecting services helps reuse logic and keeps components focused on UI.

Which of the following is NOT a way to inject a service in Angular?

A Using the inject() function

B Using the new keyword inside the component

C Using constructor parameters

D Using the @Inject decorator on a property

Using new keyword manually bypasses Angular's dependency injection system and is not recommended.

Where should you provide a service to make it available application-wide?

A In the CSS file

B Only inside the component

C In the component's template

D In the root injector (providedIn: 'root')

Providing a service in the root injector makes it available throughout the app.

Explain how to inject a service into a standalone Angular component and why this method is useful.

Think about how Angular 17 changed dependency injection for standalone components.

Describe the role of the @Injectable decorator in Angular services and how it relates to dependency injection.

Consider what makes a class a service Angular can inject.