Executing a component method from a service class in Angular

When trying to call a component method from a service class, an error is encountered: 'ERROR TypeError: Cannot read property 'test' of undefined'. Although similar issues have been researched, the explanations mostly focus on component-to-component calling, leaving confusion in understanding.

Here is an example:

Testcomponent.ts
@Component({
  selector:'component'
})
export class Testcomponent{

  test(){ 
    console.log('test method');
  }
}
Testservice.ts
@Injectable()

export class Testservice {

private testcomp: Testcomponent;

// service method
dummy(){
  //trying to call component method
  testcomp.test();
  }
}

This approach of calling the component method raises doubts about its correctness. Assistance is needed to understand the proper way to achieve this task.

Further research on Stack Overflow did not provide a clear understanding: How to call component method from service? (angular2)

Answer №1

Check out the code snippet below for an example. You can also find more information at this link

export class ExampleComponent {

  constructor(private exampleService: ExampleService) {
    this.exampleService.exampleComponent$.subscribe(res => {
      this.exampleMethod()
    })
  }

  exampleMethod() {
    console.log('This is an example method');
  }
}

export class ExampleService {

  private exampleComponentSource = new Subject<boolean>();

  // Observable string streams
  exampleComponent$ = this.exampleComponentSource.asObservable();


  // Service method
  dummy() {
    // Trying to call a component method 
    this.exampleComponentSource.next(null);
  }
}

Answer №2

To properly import a subject and emit values from a service, follow these steps:

@Injectable()
import { Subject } from 'rxjs';

export class DataService {

  dataSubject = new Subject();


// Service method
sendData(){
      this.dataSubject.next('hello from service');
  }
}

In your component, subscribe to the event like so:

@Component({
  selector:'app-component'
})
import {DataService}  from 'data.service';
export class AppComponent{
        constructor(private dataService: DataService) {
   }

  fetchData(){ 
  this.dataService.dataSubject.subscribe((data)=>{
   console.log(data);
    });

  }
}

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Is it possible to eliminate auxiliary routes in Angular 4?

Recently, I came across an interesting scenario with two <router-outlet> tags, one with a name property. To test this, I set up the following router mapping: export const routing = [ {path:'', pathMatch:'full', component:E ...

Alternative for using useRouteMatch to retrieve parameters

I'm currently refactoring this code and struggling to find a suitable replacement for this section. This is due to the react-router-dom v6 no longer having the useRouteMatch feature, which I relied on to extract parameters from the URL: import React, ...

The array is not empty but the length is being displayed as zero

I am facing an issue in my project where I can successfully print the array in console, but I am unable to retrieve the length and access the first element. Here is the code snippet: checkout.component.ts: ngOnInit() { this.booksInCheckout = this.ch ...

Tips for integrating jsPDF with Angular 2

Encountering Error: jsPDF is not defined, while implementing the code below: import { Component, OnInit, Inject } from '@angular/core'; import 'jspdf'; declare let jsPDF; @Component({ .... providers: [ { provide: 'Window&a ...

attempting to pass a boolean type through props resulting in a type error

Hey, check out this component I created: import * as Styled from './styles'; export type HeadingProps = { children: React.ReactNode | string; colorDark: boolean; }; export const Heading = ({ children, colorDark }: HeadingProps) => { re ...

Tips for implementing a guard feature using a modal window

I am looking to implement a dialog window with yes and no responses when clicking on a router link. If the user selects 'yes', I want to pass through the canActivate guard. The issue arises when returning to the same router with the guard in pla ...

Guide on displaying the length of an observable array in an Angular 2 template

I am working with an observable of type 'ICase' which retrieves data from a JSON file through a method in the service file. The template-service.ts file contains the following code: private _caseUrl = 'api/cases.json'; getCases(): Obs ...

Tips for accessing a RouterState from the @ngxs/router-plugin before and during the initialization of other states

Previously, in an Angular 8.0.0 and 3.5.0 NGXS application, I successfully retrieved the RouterState using SelectSnapshot from the @ngxs/router-plugin within other states before component rendering. However, in my latest application, the RouterState now re ...

What are the conditions for Jasmine's .toHaveBeenCalledWith to match the parameters?

I'm working on an Angular service along with its Jasmine test. The test is calling f1() and spying on f2(). The function f2 takes a variable v2 and updates it by setting field 'a' to 3. I expected the function f2 to be called with v2 (as def ...

Choosing the primary camera on a web application with multiple rear cameras using WebRTC

Having a bit of trouble developing a web app that can capture images from the browser's back camera. The challenge lies in identifying which camera is the main one in a multi-camera setup. The issue we're running into is that each manufacturer u ...

Continuously encountering CORS errors despite activating them, using .NET Core in conjunction with an Angular client

I recently encountered a CORS issue in my .NET Core 3.0 Web API project despite having enabled CORS in the startup file. Here's how I configured it: ConfigureService services.AddCors(options => { options.AddPolicy("AllowOrigin", builder => b ...

The type 'Navigator' does not have the property 'userAgentData' in its definition

Since I'm looking to minimize the information provided by navigator.userAgent, I decided to migrate to User-Agent Client Hints. However, I've encountered an error while attempting to do so: https://i.stack.imgur.com/lgIl7.png Could someone plea ...

Inference in Typescript - Detecting unknown key in an object

I am struggling to implement type inference from a props object that is passed to a component and then used in a render function. While I can retrieve the keys of the object correctly, all types are being interpreted as unknown. I need some assistance in f ...

Angular 2 code test coverage

Looking to calculate the code coverage of my Angular 2 code. Wondering if there are any plugins available for VS Code or WebStorm that can assist with this. My unit testing is done using Jasmine and Karma. ...

Steps for personalizing the dataset on a PrimeNG bar graph

I'm currently working with primeng in an Angular project and I need to create a bar chart where the last two horizontal bars have different colors. Right now, the last two bars are incorrectly being assigned to represent dogs and cats. My goal is to ...

Look for identical values within a nested array

My data consists of a nested array where each element has a property called name, which can only be either A or B. I need to compare all elements and determine if they are all either A or B. Here is an example of the input: [ { "arr": { "teach ...

Retrieve the raw text from the input field instead of the date object

Below is the HTML code for an input field: <div class="input-group input-group-md"> <input id="date" name="date" [readOnly]="disabled" type="text" placeholder="M0/d0/0000 Hh:m0:s0" [placeholder]="pl ...

Obtaining additional information for Observable<Object[]>

I have a scenario where I am working with a service that returns Observable<Object[]>. Each Object in the array has a subObjectId property. My goal is to populate the object's subObject property with data retrieved from another service. How can ...

Is there an automatic bottom padding feature?

Currently, I am facing a challenge in fitting the loader into the container without it being overridden by the browser. Using padding-bottom is not an ideal solution as it results in the loader appearing un-resized and unprofessional. Any suggestions or co ...

Refreshing a component without having to reload the entire page in Angular4: A step-by-step guide

I have an application built with Angular 4 that consists of two components - one for adding items and another for viewing them. I am facing an issue where the view page does not update with the new item added. Although I can see the updated data source, th ...