How does a component receive dependencies through the constructor?

AngularJunior~1 min read

In Angular, a component receives dependencies through Dependency Injection (DI), by passing them into the class constructor.

How it works

Parameters with the types of the services the component needs are added to the component's constructor.
Angular checks the injector (module or component), looks for the matching service, and creates an instance of it (or takes an existing one).
After that, the service becomes available in the component through the property defined in the constructor.

Example:

typescript

import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-example',
  template: `<p>{{ data }}</p>`
})
export class ExampleComponent {
  data: string;

  constructor(private dataService: DataService) {
    this.data = this.dataService.getData();
  }
}

Conclusion: Angular automatically creates and injects service instances through the constructor, freeing the developer from manually creating dependencies.

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How does a component receive dependencies through the constructor?

#How it works

Short Answer

How it works