# Kotlin Flows - collect vs collectLatest

Kotlin Coroutines and Flows make asynchronous programming really easy to understand. And in this post, we'll look at two important but slightly different operators - `collect` and `collectLatest`


Both `collect` and `collectLatest` are **terminal operators** *i.e.* they will actually **start** the flow.

Now let's see how are they different?

First of all, let's build a flow

```kotlin
fun intFlow() = flow {
    (1..5).forEach {
        delay(50)
        println("Flowing $it...")
        emit(it)
    }
}
```

Please note that there is a delay of *50 ms* in the builder. 

### `collect {  }` 

```kotlin
suspend fun main() {
    intFlow().collect {
        delay(100)
        println("\t\t\t\t$it received")
    }
}
```
Note that there is a delay of *100 ms* in the collector. Next, let's see the execution: 

```text
Flowing 1...
				1 received
Flowing 2...
				2 received
Flowing 3...
				3 received
Flowing 4...
				4 received
Flowing 5...
				5 received
```

At first look, you might not see it but look closely. In this case, the builder *suspends* until the collector is ready for the next value. That is evident because collector delays for *100 ms* while builder only delays for *50*.

Now, let's see what happens with `collectLatest`

### `collectLatest {  }`

```kotlin
suspend fun main() {
    intFlow().collectLatest {
        delay(100)
        println("\t\t\t\t$it received")
    }
}
```

```text
Flowing 1...
Flowing 2...
Flowing 3...
Flowing 4...
Flowing 5...
				5 received
```

In this case, the collector is canceled when it receives a new value from the builder and starts with that value. This is clear because, after *50 ms*, the builder provides a new value to the collector.

# How to choose between them?

The tradeoff between `collect { ... }` and `collectLatest { ... }` is fairly straightforward. If you need to process all the values you receive you should use `collect`, if you want only the "latest" value to be processed, use `collectLatest`.

This is all, if you found this article helpful, please drop a like. :)

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