WEBVTT

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Welcome back.

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We used dry sand and a way to close functions, but there are errors here.

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None of the following candidates is applicable because of receiver type mismatch.

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Okay.

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And if we hover here unresolved reference trace.

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This type of error occurs because these functions need to be called within the proper coroutine context

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or because you are missing necessary imports.

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Let's try to use the callback.

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So here equals to callback flow and scroll down.

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The errors are solved.

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But what are try send and await close functions and why we use them in Kotlin coroutines, particularly

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when working with flows and callback based APIs like Firebase Firestore.

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Try sand and await close serve specific purposes to bridge between callback style APIs and reactive

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streams flow in this this function.

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Get all markers from Firestore.

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We used the reactive streams of the flow and the callback style API, which is the listener, and the

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Firebase collection.

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The bridge between them is try and await close functions.

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Try send non-blocking emission of values to a flow from a callback.

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I want from you to write those notes down.

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The purpose of try sand is non-blocking emission of values to a flow from a callback used in callback

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flow or mutable shared flow to safely emit values without suspending the coroutine.

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Why we use it Firebase's ad snapshot listener uses callbacks, but we want to expose data as a flow.

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Try send allows emitting values from the callback into the flow.

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Non suspending regular sand suspends if the buffer is full, dry sand is non-blocking and returns immediately

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true if the value was emitted successfully.

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False if the buffer is full or the flow is closed, a wait close suspends the coroutine until the flow

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is canceled, then runs clean up code, ensuring resources like Firebase Firestore listeners are released

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when the flow is no longer needed.

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Resource cleanup means the callback based APIs like Firestore listeners need to be unregistered to avoid

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leaks.

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Await close provides a way to run cleanup when the flow collection stops.

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Flow lifetimes in Jetpack Compose flows collected via collect as a state function are canceled when

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the composable leaves the composition and await close function ensures that Firebase Firestore listener

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is removed at the right time.

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So here the coroutine suspends the await close until either the flow is canceled.

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Triggered the cleanup block or close is called explicitly.

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And here we need to use close and use the error.

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Okay.

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So this will cancel the flow and close it.

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Okay.

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One last thing we need to solve is the return type of the flow.

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Here we change it from list of destination marker to flow of list of destination marker.

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Let me go back to the marker repository and change it to a flow of list of destination marker.

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Import flow.

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And here we go.

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So this is the usage of wait close and try send functions.