124. Using Services for Pushing Data from A to B

Jul 15, 2026 05:15 · 3:08 · English · Whisper Turbo · 2 Speaker

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Indeks Kuliah

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

In the last lecture,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

we basically finished our shopping list service,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

but here's one thing which is not working.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

I can click this Add button as often as I want.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

I don't get an error,

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but I also don't see it getting added to this list.

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The reason for this is that when

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we call Get Ingredients,

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which we of course do to populate this list,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

we only get a slice of the ingredients array,

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so we get a copy.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

Therefore, once we add a new ingredient,

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which you of course don't add to the copy but to the original array,

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that is not reflected in our components where we only have that

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copy to work with.

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S… Speaker 2 (124. Using Services for Pushing Data from A to B)

Now,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

there are a couple of ways of solving this.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

For the easiest solution,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

you could remove slice and that's not necessarily bad.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

You would then simply return the original array.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

And if you are sure you don't accidentally edit it somewhere,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

this might not be wrong.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

I choose this approach here,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

though, because I want to show you a different solution.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

We basically have to inform our component

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

that new data is available.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

So I will simply add a new event

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

emitter here,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

and I'll name it ingredients changed,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

and I'll set this to,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

or I'll,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

of course, set this to a new event emitter to be imported from at

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AngularCore.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

This event emitter now,

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can emit our ingredient array.

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So the type it will pass on is an array of ingredients.

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And now here,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

whenever we change this array,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

we simply call this ingredients changed and

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emit a new event.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

And we of course pass a value here,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

our original ingredients array,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

though to be precise,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

again, only a copy of it.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

So now we always have the right ingredients

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

array in the service and we inform other interested

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

components about that change in the event we're emitting here.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

So now in the shopping list component,

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besides getting the ingredients at that point of time we load

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the app,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

I also want to reach out to my shopping list service and

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

simply subscribe to that ingredients changed event.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

So now whenever ingredients change,

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

I know that I will get them.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

This will be of type ingredient array here as we learned.

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

And now I can use them here in the body of this anonymous function

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I'm passing to subscribe.

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And here I can now simply set this

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ingredients equal to the ingredients I got here.

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And with this change in place,

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now if we let the application reload here

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and go to shopping list and now I add bread and

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

now you see it gets added here again without any issues because

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S… Speaker 1 (124. Using Services for Pushing Data from A to B)

now we're getting informed that something changed.

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