In concurrent programming, different parts of a program can run independently of each other to make better use of resources like CPU time and memory. A common challenge with concurrent programming is coordinating the different parts of the program to avoid conflicts.
Kotlin's channels and flow provide a helpful way to manage concurrent programming by allowing different parts of the program to communicate with each other. Channels are like pipes that can carry data from one part of the program to another, and flow is a way of managing the flow of data through those channels.
Here's a simple example of how channels and flow can be used to coordinate different parts of a program. We have a program that needs to print out a list of numbers, but we want to do it in two separate parts: one part to print the numbers themselves, and another part to print a message after the numbers have been printed.
We can use a channel to send the numbers from the first part of the program to the second part, and use flow to ensure that the message is only printed after all the numbers have been sent.
import kotlinx.coroutines.*
import kotlinx.coroutines.flow.*
fun main() {
val numbers = (1..5).asFlow() // 1
val printMessage = numbers.onEach { println(it) } // 2
.collect { println("Done printing numbers") } // 3
runBlocking {
launch { printMessage.collect() } // 4
}
}
asFlow
extension function.onEach
transformation to print each number as it flows through the channel.collect
transformation to wait until all the numbers have been printed, then print a message.This example shows how channels and flow can be used to coordinate different parts of a program. Channels allow different parts of the program to communicate with each other, and flow provides a way to manage the flow of data through those channels.