139. An Important Note about Route Observables

Jul 15, 2026 05:34 · 2:42 · English · Whisper Turbo · 2 කථානායක

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S… Speaker 2 (139. An Important Note about Route Observables)

In the last lecture,

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S… Speaker 2 (139. An Important Note about Route Observables)

we learned how we can subscribe to our params to update them

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S… Speaker 2 (139. An Important Note about Route Observables)

or to react to any changes to them and update our page if we already

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are on that page.

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S… Speaker 2 (139. An Important Note about Route Observables)

And we set up this subscription using observables and this works

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S… Speaker 2 (139. An Important Note about Route Observables)

fine and you don't have to change anything here.

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S… Speaker 2 (139. An Important Note about Route Observables)

I want to bring something to your attention though.

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S… Speaker 2 (139. An Important Note about Route Observables)

The fact that you don't have to add anything else to this

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S… Speaker 2 (139. An Important Note about Route Observables)

component here simply is because Angular

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S… Speaker 2 (139. An Important Note about Route Observables)

does something for you in the background which is super

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S… Speaker 2 (139. An Important Note about Route Observables)

important.

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S… Speaker 2 (139. An Important Note about Route Observables)

It cleans up the subscription you set up here whenever

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S… Speaker 2 (139. An Important Note about Route Observables)

this component is destroyed.

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S… Speaker 2 (139. An Important Note about Route Observables)

Because if it wouldn't do this,

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S… Speaker 2 (139. An Important Note about Route Observables)

what are you doing here?

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S… Speaker 2 (139. An Important Note about Route Observables)

You're subscribing to parameter changes and let's say you then leave this

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component and later you come back.

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S… Speaker 2 (139. An Important Note about Route Observables)

Well, once you left,

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S… Speaker 2 (139. An Important Note about Route Observables)

this component will be destroyed,

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S… Speaker 2 (139. An Important Note about Route Observables)

and when you come back,

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S… Speaker 2 (139. An Important Note about Route Observables)

a new one will be created.

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S… Speaker 2 (139. An Important Note about Route Observables)

But this subscription here will always live on in memory

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S… Speaker 2 (139. An Important Note about Route Observables)

because it's not closely tied to your component.

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S… Speaker 2 (139. An Important Note about Route Observables)

So if the component is destroyed,

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S… Speaker 2 (139. An Important Note about Route Observables)

the subscription won't.

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S… Speaker 1 (139. An Important Note about Route Observables)

Now,

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S… Speaker 2 (139. An Important Note about Route Observables)

it will be here because Angular handles this destroying of

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S… Speaker 2 (139. An Important Note about Route Observables)

the subscription for you.

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S… Speaker 2 (139. An Important Note about Route Observables)

But theoretically,

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S… Speaker 2 (139. An Important Note about Route Observables)

you might want to implement the onDestroy lifecycle hook,

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S… Speaker 2 (139. An Important Note about Route Observables)

importing it from atAngularCore,

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S… Speaker 1 (139. An Important Note about Route Observables)

Therefore,

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S… Speaker 2 (139. An Important Note about Route Observables)

you have to implement ng on destroy.

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S… Speaker 2 (139. An Important Note about Route Observables)

And then you could store this subscription here in some

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S… Speaker 1 (139. An Important Note about Route Observables)

property.

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S… Speaker 2 (139. An Important Note about Route Observables)

Let's name it params subscription,

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S… Speaker 2 (139. An Important Note about Route Observables)

which will be of type subscription.

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S… Speaker 2 (139. An Important Note about Route Observables)

And subscription needs to be imported from rxjs

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S… Speaker 2 (139. An Important Note about Route Observables)

subscription.

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S… Speaker 2 (139. An Important Note about Route Observables)

rxjs is the package offering all this observables

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S… Speaker 2 (139. An Important Note about Route Observables)

functionality.

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S… Speaker 2 (139. An Important Note about Route Observables)

As I mentioned,

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S… Speaker 2 (139. An Important Note about Route Observables)

it's not shipping with Angular,

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S… Speaker 2 (139. An Important Note about Route Observables)

but Angular is using this package.

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S… Speaker 2 (139. An Important Note about Route Observables)

So this type here,

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S… Speaker 2 (139. An Important Note about Route Observables)

this subscription,

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S… Speaker 2 (139. An Important Note about Route Observables)

this paramSubscription property is now bound to this

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S… Speaker 2 (139. An Important Note about Route Observables)

subscription we're setting up here when calling subscribe.

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S… Speaker 2 (139. An Important Note about Route Observables)

This returns us this subscription.

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S… Speaker 2 (139. An Important Note about Route Observables)

And once the component gets destroyed,

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S… Speaker 2 (139. An Important Note about Route Observables)

we could now access the subscription and unsubscribe.

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S… Speaker 1 (139. An Important Note about Route Observables)

And again,

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S… Speaker 2 (139. An Important Note about Route Observables)

because it's important,

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S… Speaker 2 (139. An Important Note about Route Observables)

you don't have to do this.

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S… Speaker 2 (139. An Important Note about Route Observables)

You can leave it as it was before because Angular will do this for

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S… Speaker 2 (139. An Important Note about Route Observables)

you regarding these route observables.

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S… Speaker 2 (139. An Important Note about Route Observables)

But if you add your own observables,

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S… Speaker 2 (139. An Important Note about Route Observables)

and I will come back to this in the observables section following this section.

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S… Speaker 2 (139. An Important Note about Route Observables)

You have to unsubscribe on your own.

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S… Speaker 2 (139. An Important Note about Route Observables)

And I just wanted to bring it to your attention because it's always super important to

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S… Speaker 2 (139. An Important Note about Route Observables)

understand what's happening behind the scenes.

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S… Speaker 2 (139. An Important Note about Route Observables)

Again, it's not necessary here,

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S… Speaker 2 (139. An Important Note about Route Observables)

but it doesn't hurt to also do it manually too here.

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S… Speaker 2 (139. An Important Note about Route Observables)

It won't add anything bad to your app by doing it like this.

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