The 'unsubscribe' property is not found on the 'Observable<DataSnapshot>' type

I am facing a typescript error in my code, specifically in the tslint plugin of Atom editor. Unfortunately, I am struggling to determine how to correctly set the type.

Error message: https://i.sstatic.net/VU3ee.png

Here is the code snippet for the chat component:

  private _chatObserver: Observable<firebase.database.DataSnapshot>

  otherMethod () {
        this._chatObserver = this._chat.observe(alarmId)
        this._chatObserver.subscribe(
          (messageSnap: firebase.database.DataSnapshot) => {
            this.messages.push(messageSnap.val())
          },
          error => {throw error})
    }

    ionViewDidLeave() {
       this._chatObserver.unsubscribe() 
    }

And here is the code snippet for the _chat provider:

  public observe (alarmId){
    let messagesRef = this._ref.child(`alarms/${alarmId}/messages`)

    const observable = Observable.create(observer => {
      messagesRef.on('child_added',(messageSnap) => {
            observer.next(messageSnap)
        },
        (error) => observer.error(error)
      )
      return () => {
        messagesRef.off('value')
      };
    });

    return observable
  }

Answer №1

To cancel your subscription, you must use the unsubscribe method directly on the subscription object. To do this, start by declaring a private variable at the top like so:

private _subscriptionToCancel;

Then, within your specificMethod:

this._subscriptionToCancel = this._specificObserver.subscribe(...);

Finally, when terminating or leaving, make sure to call the unsubscribe method on the subscription object:

this._subscriptionToCancel.unsubscribe();

Answer №2

When you subscribe to an observable, it will provide you with a subscription object that includes the unsubscribe() method

private _chatObserver: Observable<firebase.database.DataSnapshot>
private _subscription:Subscription
otherMethod () {
    this._chatObserver = this._chat.observe(alarmId)
    this._subscription=this._chatObserver.subscribe(
      (messageSnap: firebase.database.DataSnapshot) => {
        this.messages.push(messageSnap.val())
      },
      error => {throw error})
}

ionViewDidLeave() {
   this._subscription.unsubscribe() 
}

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

Executing POST calls to a Google Apps Script

Everything was running smoothly. I managed to set up an endpoint using Google Apps Script that allowed end users to send a message to me (or another contact) and receive a copy of that message as well. The code for the POST request looked something like ...

The data type 'string | null | undefined' cannot be assigned to the data type 'string | undefined'

In my Angular application using Typescript, I have the following setup: userId?: number; token?: string; constructor(private route: ActivatedRoute) { this.route.queryParamMap.subscribe( (value: ParamMap) => { this.userId = val ...

Oops! An issue occurred during the `ng build` command, indicating a ReferenceError with the message "Buffer is not defined

I'm facing an issue while trying to utilize Buffer in my angular component ts for encoding the Authorization string. Even after attempting npm i @types/node and adding "node" to types field in tsconfig.json, it still doesn't compile with ng buil ...

Improving the way of handling CLOB_Column in DBMS.SUBSTR

I've recently been tasked with developing a backend application using Node.js, TypeScript, and an Oracle SQL server. Within this application, there is a database table named TableA which consists of columns: ID (NUMBER) & App_Log_File (CLOB). The App ...

What is the method to retrieve a generic TypeScript type within a function's code block?

When attempting to utilize a generic type within a TypeScript function: const func: <T extends number>() => void = () => { const x: T = 1 } An error message is generated: Cannot find name 'T'. TS2304 69 | const func: <T e ...

What is the method for returning a string array?

My query is about how to return a string[]. Currently, TypeScript is throwing an error because each element of the array has a type of ( T[keyof T] extends readonly (infer InnerArr)[] ? InnerArr : T[keyof T] ). How can I accept the 'property' arg ...

Select characteristics with designated attribute types

Is there a way to create a type that selects only properties from an object whose values match a specific type? For example: type PickOfValue<T, V extends T[keyof T]> = { [P in keyof (key-picking magic?)]: T[P]; }; I am looking for a solution w ...

Get the dynamic type as the return value in a TypeScript abstract class method with generic type T

Within my codebase, I have created an abstract class: export abstract class Filters<P> { protected field: string; protected constructor(field: string) { this.field = field; } protected abstract getFilter(): P; } Additionally, there is ...

Error: User authentication failed: username: `name` field is mandatory

While developing the backend of my app, I have integrated mongoose and Next.js. My current challenge is implementing a push function to add a new user to the database. As I am still relatively new to using mongoose, especially with typescript, I am followi ...

Creating object interfaces in TypeScript dynamically based on function parameters

I'm currently working on a small project that involves creating lists of products in a certain format. For example: let products = createList( new Product('product1'), new Product('product2') ) When it comes to accessing a s ...

Detecting changes in Angular custom form controls when using `mat-select` with the `selectionChange` event

I'm facing an issue with my custom form control that includes a mat-select element I've been attempting to listen for the change event in the parent component However, my onTouchedCallback doesn't seem to be functioning for some reason Wh ...

Retrieve the IP Address using Express and GraphQL

Seeking assistance here! I recently made the switch from using rest to gql, but encountered an issue along the way. In my previous setup with rest, I was able to retrieve the user's IP address using req.ip. However, when trying to implement this in th ...

I am faced with a challenge involving an asynchronous function and the best approach to executing it synchronously

I devised the following plan: // Primary Function to Follow // Capture necessary local data // Transform into required editable format // Iterate through user's local images // Append image names to converted d ...

Get the HeatMap ngx swimlane chart as an image by downloading or exporting it

Is there a way to download or export the HeatMap ngx swimlane chart as an image? If you need a solution for downloading the chart as an image, please refer to this Plunker URL: https://plnkr.co/edit/2rtX5cueg2hlzmztUbkH?p=preview I am looking for any opt ...

Implementing conditional asynchronous function call with identical arguments in a Typescript React project

Is there a way in React to make multiple asynchronous calls with the same parameters based on different conditions? Here's an example of what I'm trying to do: const getNewContent = (payload: any) => { (currentOption === myMediaEnum.T ...

update the value of a specific document in Firestore by specifying its

Is there a way to update document values in a Firestore collection for multiple records without manually specifying each document ID? Currently, I have a method that works for updating individual documents using their IDs, but what if I need to update a la ...

Switch the visibility of all local variables in *ngFor from an external loop

Imagine having an *ngFor loop where a local variable is defined like this: <div *ngFor="let item of items"> <p>{{item.name}}</p> <div *ngIf="item.colorVisible">{{item.color}}</div> <button (click)="item.colorVisible ...

When running the test, a "is not defined" ReferenceError occurs in the declared namespace (.d.ts) in ts-jest

When running typescript with ts-jest, the application functions properly in the browser but encounters a ReferenceError: R is not defined error during testing. The directory structure: |--app | |--job.ts |--api | |--R.d.ts |--tests | |--job.test.ts ...

Broadcast signals to an overarching frame

I have successfully embedded a chatbot (Angular 14 app) in an iframe and now I need to determine whether the frame should be minimized so it can fit within the parent container. My goal is to send custom events to the receiving frame. let iframeCanvas = do ...

Combining String Literal Types with a regular string type

Is there a way to utilize the intellisense feature of TypeScript for predefined colors in my component's prop, while still allowing users to input their own hex color codes? type PREDEFINED_COLORS = 'success' | 'error' | 'info ...