What is the best way to inject a service instance into the implementation of an abstract method?

Question

What is the best way to inject a service instance into the implementation of an abstract method?

In my Angular application, I have a service that extends an abstract class and implements an abstract method.

@Injectable({
  providedIn: 'root',
})
export class ClassB extends ClassA { 

constructor(
    private service : ExampleService) {
    super();
  }

  abstractMethod() {
   //this.service returns undefined here
  }

} 

export abstract class ClassA { 

  abstractMethod();
  
  otherMethod() { 
    this.abstractMethod();
  }
}

Nevertheless, in the constructor of ClassB, I face the challenge of injecting a service to be used within the abstract method.

The abstract method is called within "otherMethod()" in the Abstract class. Since the abstractMethod() has no implementation in the Parent class, it expects to find its implementation in the child class, but currently, it returns undefined.

How can I successfully utilize a service instance within the abstractMethod()?

To elaborate, I am striving to access a service instance inside "abstractMethod()", yet it currently results in returning undefined.

javascript angular typescript

Answer 1

Answer №1

Reasons for Code Failure

this.service is invoked in abstract class ClassA.
ClassA does not recognize a service property.
Only ClassBService has access to the service property because it is marked as private.

Solution

Add a service property to ClassA.
Change the scope of your service property to either protected or public.

The following code performs similar functionality to what you desire

    import { Injectable } from "@angular/core";
    import { HelloService } from "./hello.service";
    
    abstract class ClassA {
      protected service: HelloService;
      public hello() {}
    
      protected say_hello() {
        this.service.hello();
      }
    }
    
    @Injectable()
    export class ClassBService extends ClassA {
      constructor(protected service: HelloService) {
        super();
      }
    
      public hello() {
        this.say_hello();
      }
  }

Answer 2

Reasons for Code Failure

this.service is invoked in abstract class ClassA.
ClassA does not recognize a service property.
Only ClassBService has access to the service property because it is marked as private.

Solution

Add a service property to ClassA.
Change the scope of your service property to either protected or public.

The following code performs similar functionality to what you desire

    import { Injectable } from "@angular/core";
    import { HelloService } from "./hello.service";
    
    abstract class ClassA {
      protected service: HelloService;
      public hello() {}
    
      protected say_hello() {
        this.service.hello();
      }
    }
    
    @Injectable()
    export class ClassBService extends ClassA {
      constructor(protected service: HelloService) {
        super();
      }
    
      public hello() {
        this.say_hello();
      }
  }

What is the best way to inject a service instance into the implementation of an abstract method?

Answer №1

Similar questions

Automatically update the table in Python Flask every minute

Utilizing the map function in React to create a button reference

Retrieve objects from an array that contain a certain specified key

Rearrange an element in an array from last to first position using typescript

Are we looking at a declaration of an arrow function? Is this concept even real?

Evaluate the functionality of an Angular controller method that interacts with the Document Object Model (

How to include images in a PDF using jspdf without encountering issues with Adobe Reader?

Stopping the ability to navigate within an Ionic application

Why do ES6 classes fail to set properties when an overloaded function is called within the constructor of the parent class?

Why isn't Sequence.js Slider automatically playing?

Detecting changes to DOM elements without using jQueryResponding to DOM element

Tips for invoking a PHP function with jquery

Tips for effectively managing relationships in a RESTful API

Getting JSON data from an Angular JS controller can be achieved by utilizing the built-in

Employing a while loop within the context of a Promise

Obtain the name of the client's computer within a web-based application

Transforming JQuery text upon selecting preloaded content with fire

Emulate clicking a radio button (using PHP and JS)

Exploring the Power of Two jQuery Ajax Functions in Your Script

Switching up the content of an HTML page with JavaScript or JQuery: what you need