Steps for setting up a Subscription instanceWould you like me to

Question

Steps for setting up a Subscription instanceWould you like me to

I am currently utilizing a Subscription in Angular to extract a parameter from the route. Below is the code snippet:

import { Component, OnInit, OnDestroy } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { Subscription} from 'rxjs';


@Component({
    selector: 'farm-house',
    templateUrl: './house.component.html',
    styleUrls: ['./house.component.scss']
})
export class GreenhouseComponent implements OnInit, OnDestroy {
    
    private routeSub: Subscription;
    id: string;

    constructor(private route: ActivatedRoute) {
        this.id = "";
    }

    ngOnInit(): void {
        this.routeSub = this.route.params.subscribe(params => {
            this.id = params['id'];
        });
    }

    ngOnDestroy() {
        this.routeSub.unsubscribe();
    }
}

However, I encountered an issue where the compiler flagged:

Property 'routeSub' has no initializer and is not definitely assigned in the constructor.

Hence, my inquiry revolves around finding the optimal method to initialize a Subscription object?

angular typescript rxjs

Answer 1

Answer №1

I've found an alternate solution by utilizing the Subscription.EMPTY method mentioned in this thread.

import { Component, OnInit, OnDestroy } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { Subscription} from 'rxjs';


@Component({
    selector: 'farm-house',
    templateUrl: './house.component.html',
    styleUrls: ['./house.component.scss']
})
export class GreenhouseComponent implements OnInit, OnDestroy {
    
    private routeSub: Subscription;
    id: string;

    constructor(private route: ActivatedRoute) {
        this.routeSub = Subscription.EMPTY;
        this.id = "";
    }

    ngOnInit(): void {
        this.routeSub = this.route.params.subscribe(params => {
            this.id = params['id'];
        });
    }

    ngOnDestroy(): void {
        if(this.routeSub) {
            this.routeSub.unsubscribe();
        }
    }
}

Answer 2

I've found an alternate solution by utilizing the Subscription.EMPTY method mentioned in this thread.

import { Component, OnInit, OnDestroy } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { Subscription} from 'rxjs';


@Component({
    selector: 'farm-house',
    templateUrl: './house.component.html',
    styleUrls: ['./house.component.scss']
})
export class GreenhouseComponent implements OnInit, OnDestroy {
    
    private routeSub: Subscription;
    id: string;

    constructor(private route: ActivatedRoute) {
        this.routeSub = Subscription.EMPTY;
        this.id = "";
    }

    ngOnInit(): void {
        this.routeSub = this.route.params.subscribe(params => {
            this.id = params['id'];
        });
    }

    ngOnDestroy(): void {
        if(this.routeSub) {
            this.routeSub.unsubscribe();
        }
    }
}

Answer 3

Answer №2

Simply put,

private routeSub: Subscription = new Subscription

That's the solution that did the trick for me.

Answer 4

Simply put,

private routeSub: Subscription = new Subscription

That's the solution that did the trick for me.

Answer 5

Answer №3

It's usually sufficient to verify the subscription before unsubscribing in most cases.

 ngOnDestroy() {
     if(this.routeSub) {
       this.routeSub.unsubscribe();
     }
 }

In your particular situation, there is no need to initialize the subscription because you have already called the subscribe method in ngOnInit(). The error may occur because you are directly calling unsubscribe() on a Subscription without first checking if it has been initialized or not.

Answer 6

It's usually sufficient to verify the subscription before unsubscribing in most cases.

 ngOnDestroy() {
     if(this.routeSub) {
       this.routeSub.unsubscribe();
     }
 }

In your particular situation, there is no need to initialize the subscription because you have already called the subscribe method in ngOnInit(). The error may occur because you are directly calling unsubscribe() on a Subscription without first checking if it has been initialized or not.

Answer 7

Answer №4

Method 1:

In this method, there is only one subscription to handle.

private routeSub?: Subscription;
    ngOnInit(): void {
        this.routeSub = this.route.params.subscribe(params => {
            this.id = params['id'];
        });
    }

    
    ngOnDestroy(): void {
       // Instead of using a separate if statement, use ? for better readability
        this.routeSub?.unsubscribe();
    }

Method 2 involves handling multiple subscriptions and cleaning them up collectively:

    private destroyed$ = new Subject<boolean>();

Somewhere() {
combineLatest([userService.spaceName$, userService.userName$])
      .pipe(takeUntil(this.destroyed$))
      .subscribe(([space, username]) => {do something...}
    }

ngOnDestroy() {
    this.destroyed$.next(true);
    this.destroyed$.complete();
  }

The third method is often considered the most effective approach:

myObservable$: Observable<myInterface>;

ngOnInit() {
   this.myObservable$ = this.myservice.someObservable$;
}

...    html ...
<ng-container *ngIf='myObservable$ | async as list; else simpleInput'>

This final process is compatible with onPush and ensures that you never forget to unsubscribe.

It's worth noting that the first method is useful when subscribing and unsubscribing are done together in a single call, and it can also be combined with the second method:

pollUser(): void {
    // Unsubscribe if already subscribed or skip if not.
    this.subscription?.unsubscribe();

    this.subscription= this.someservice(serviceParameters)
      .pipe(takeUntil(this.destroyed$))
      .subscribe(result => {
            this.useResult = result;
        });
    }

Answer 8

Method 1:

In this method, there is only one subscription to handle.

private routeSub?: Subscription;
    ngOnInit(): void {
        this.routeSub = this.route.params.subscribe(params => {
            this.id = params['id'];
        });
    }

    
    ngOnDestroy(): void {
       // Instead of using a separate if statement, use ? for better readability
        this.routeSub?.unsubscribe();
    }

Method 2 involves handling multiple subscriptions and cleaning them up collectively:

    private destroyed$ = new Subject<boolean>();

Somewhere() {
combineLatest([userService.spaceName$, userService.userName$])
      .pipe(takeUntil(this.destroyed$))
      .subscribe(([space, username]) => {do something...}
    }

ngOnDestroy() {
    this.destroyed$.next(true);
    this.destroyed$.complete();
  }

The third method is often considered the most effective approach:

myObservable$: Observable<myInterface>;

ngOnInit() {
   this.myObservable$ = this.myservice.someObservable$;
}

...    html ...
<ng-container *ngIf='myObservable$ | async as list; else simpleInput'>

This final process is compatible with onPush and ensures that you never forget to unsubscribe.

It's worth noting that the first method is useful when subscribing and unsubscribing are done together in a single call, and it can also be combined with the second method:

pollUser(): void {
    // Unsubscribe if already subscribed or skip if not.
    this.subscription?.unsubscribe();

    this.subscription= this.someservice(serviceParameters)
      .pipe(takeUntil(this.destroyed$))
      .subscribe(result => {
            this.useResult = result;
        });
    }

Answer 9

Answer №5

Here is a simple example of how to manage subscriptions in Angular:

private mySubscriptions: Subscription = new Subscription()

When adding a subscription, use:

this.mySubscriptions.add()

Remember to unsubscribe when no longer needed:

ngOnDestroy() {
    this.mySubscriptions.unsubscribe()
}

Answer 10

Here is a simple example of how to manage subscriptions in Angular:

private mySubscriptions: Subscription = new Subscription()

When adding a subscription, use:

this.mySubscriptions.add()

Remember to unsubscribe when no longer needed:

ngOnDestroy() {
    this.mySubscriptions.unsubscribe()
}

Answer 11

Answer №6

When you define routeSub: any;, the compiler should not generate any errors. reference: I came across an example in this post and it worked successfully for me.

Answer 12

When you define routeSub: any;, the compiler should not generate any errors. reference: I came across an example in this post and it worked successfully for me.

Answer 13

Answer №7

No need to manually unsubscribe in this case as Angular takes care of destroying the subscription for you automatically.

Answer 14

No need to manually unsubscribe in this case as Angular takes care of destroying the subscription for you automatically.

Answer 15

Answer №8

If you want to eliminate this error, simply include

"strictPropertyInitialization": false

in your tsconfig.json

{
   "compilerOptions": {
      "strictPropertyInitialization": false,
   }
}

By doing this, you no longer have to worry about proper initialization, or you can alternatively include a second type undefined:

private routeSub: Subscription | undefined

Answer 16

If you want to eliminate this error, simply include

"strictPropertyInitialization": false

in your tsconfig.json

{
   "compilerOptions": {
      "strictPropertyInitialization": false,
   }
}

By doing this, you no longer have to worry about proper initialization, or you can alternatively include a second type undefined:

private routeSub: Subscription | undefined

Steps for setting up a Subscription instanceWould you like me to

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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