Angular Services – Sharing Logic & Data - Learn ANGULAR | Revochamp

Name: Angular Services – Sharing Logic & Data
Availability: InStock
Author: Revochamp

What is a Service?

A service is a class with a narrow, well-defined purpose. While components are responsible for the 'View', services are responsible for the 'Logic'. Common use cases include fetching data from a server, validating user input, or logging messages to a console. As an Engineering Manager, you should enforce using services to prevent 'Fat Components' and to make your business logic reusable across your entire application.

Creating a Service

You use the Angular CLI to generate a service. It creates a TypeScript class decorated with @Injectable. The providedIn: 'root' metadata is the modern standard, making the service a singleton available everywhere.

BASHRead-only

ng generate service core/project-api

ng generate service core/project-api

TypeScriptRead-only

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class ProjectApiService {
  private projects = ['Revochamp', 'Flutter Engine', 'AI Designer'];

  getProjects() {
    return this.projects;
  }
}

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class ProjectApiService {
  private projects = ['Revochamp', 'Flutter Engine', 'AI Designer'];

  getProjects() {
    return this.projects;
  }
}

Injecting and Using a Service

To use a service, you 'inject' it into a component's constructor. Angular's Dependency Injection (DI) system handles the instantiation, ensuring the component receives the correct instance of the service.

TypeScriptRead-only

@Component({ ... })
export class DashboardComponent implements OnInit {
  projectList: string[] = [];

  // Injecting the service
  constructor(private apiService: ProjectApiService) {}

  ngOnInit() {
    // Calling the service method
    this.projectList = this.apiService.getProjects();
  }
}

@Component({ ... })
export class DashboardComponent implements OnInit {
  projectList: string[] = [];

  // Injecting the service
  constructor(private apiService: ProjectApiService) {}

  ngOnInit() {
    // Calling the service method
    this.projectList = this.apiService.getProjects();
  }
}

The Component-Service Relationship

Services act as the data providers, while components act as the data consumers. This decoupling allows you to test your logic independently of the UI.

Singletons vs. Multiple Instances

By default, services provided in 'root' are singletons—one instance exists for the entire app. However, if you provide a service inside a specific component's providers array, Angular creates a new, private instance just for that component and its children.

Scope	Declaration	Behavior
Application	providedIn: 'root'	One instance shared by all (Singleton)
Module	@NgModule({ providers: [...] })	One instance shared by all in that module
Component	@Component({ providers: [...] })	New instance for every component created

Test Your Knowledge

of 3

Which decorator is used to define an Angular service?

@Component

@Module

@Injectable

@Service

of 3

What is the primary benefit of a Singleton service in Angular?

It makes the UI render faster

It allows multiple components to share the same instance and data

It prevents the use of TypeScript

It automatically generates HTML templates

of 3

Where do you typically inject a service in a component class?

In the ngOnInit method

In the component decorator

In the class constructor

In the HTML template

Frequently Asked Questions

When should I create a service?

Whenever you have logic that isn't specific to a single view. If two components need to access the same data or perform the same calculation, it belongs in a service.

Can a service inject another service?

Yes. Services can have their own dependencies. For example, a 'DataService' might inject the 'HttpClient' service to make web requests.

Is @Injectable() required for all services?

Yes. It provides the metadata that allows Angular to inject dependencies into the service's constructor. Even if the service has no dependencies now, it's a best practice to always include it.

import { Injectable } from '@angular/core'; @Injectable({ providedIn: 'root' }) export class ProjectApiService { private projects = ['Revochamp', 'Flutter Engine', 'AI Designer']; getProjects() { return this.projects; } }

@Component({ ... }) export class DashboardComponent implements OnInit { projectList: string[] = []; // Injecting the service constructor(private apiService: ProjectApiService) {} ngOnInit() { // Calling the service method this.projectList = this.apiService.getProjects(); } }

Scope

Declaration

Behavior

Application

providedIn: 'root'

One instance shared by all (Singleton)

Module

@NgModule({ providers: [...] })

One instance shared by all in that module

Component

@Component({ providers: [...] })

New instance for every component created

Test Your Knowledge

of 3

Which decorator is used to define an Angular service?

@Component

@Module

@Injectable

@Service

of 3

What is the primary benefit of a Singleton service in Angular?

It makes the UI render faster

It allows multiple components to share the same instance and data

It prevents the use of TypeScript

It automatically generates HTML templates

of 3

Where do you typically inject a service in a component class?

In the ngOnInit method

In the component decorator

In the class constructor

In the HTML template

Frequently Asked Questions

When should I create a service?

Whenever you have logic that isn't specific to a single view. If two components need to access the same data or perform the same calculation, it belongs in a service.

Can a service inject another service?

Yes. Services can have their own dependencies. For example, a 'DataService' might inject the 'HttpClient' service to make web requests.

Is @Injectable() required for all services?

Yes. It provides the metadata that allows Angular to inject dependencies into the service's constructor. Even if the service has no dependencies now, it's a best practice to always include it.

Angular Services – Sharing Logic & Data

Angular Services – Sharing Logic & Data

What is a Service?

Creating a Service

Injecting and Using a Service

The Component-Service Relationship

Singletons vs. Multiple Instances

Test Your Knowledge

Frequently Asked Questions

Need help?

Angular Services – Sharing Logic & Data

Angular Services – Sharing Logic & Data

What is a Service?

Creating a Service

Injecting and Using a Service

The Component-Service Relationship

Singletons vs. Multiple Instances

Test Your Knowledge

Frequently Asked Questions

Need help?