Singleton Services in Angular

Singleton services in Angular are services that are instantiated only once during the lifetime of an application. They provide a single instance that is shared across multiple parts of an application, ensuring data consistency and efficient resource utilization.

Understanding Singleton Services

Angular services are by default singleton services when provided at the root level. This means that there is only one instance of the service throughout the application:

// my.service.ts
import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class MyService {
  constructor() { }

  getMessage(): string {
    return 'Hello from MyService!';
  }
}

Providing Singleton Services

To provide a service as a singleton in Angular, you typically use the providedIn: 'root' option in the @Injectable decorator:

// app.module.ts
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { MyService } from './my.service';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule],
  providers: [MyService],
  bootstrap: [AppComponent]
})
export class AppModule { }

Injecting Singleton Services

Singleton services can be injected into components, directives, or other services. Angular's dependency injection system ensures that the same instance of the service is provided wherever it's injected:

// my.component.ts
import { Component } from '@angular/core';
import { MyService } from './my.service';

@Component({
  selector: 'app-my-component',
  template: '
{{ message }}
',
})
export class MyComponent {
  message: string;

  constructor(private myService: MyService) {
    this.message = this.myService.getMessage();
  }
}

Benefits of Singleton Services

Singleton services offer several benefits:

• Resource efficiency: Only one instance of the service is created and shared across the application.
• Data consistency: Since there's only one instance, changes made to the service state are visible everywhere it's injected.
• Easy management: Singleton services are managed by Angular's dependency injection system, reducing the need for manual management.

Key Points

Conclusion

Singleton services play a crucial role in Angular applications by providing shared instances that promote resource efficiency and data consistency. By understanding and leveraging singleton services, you can build scalable and maintainable Angular applications with ease.