par
fun <B, C> parZip( ctx: CoroutineContext = Dispatchers.Default, fb: Resource<B>, f: suspend (A, B) -> C): Resource<C>
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Composes two Resources together by zipping them in parallel, by running both their acquire handlers in parallel, and both release handlers in parallel.
Useful in the case that starting a resource takes considerable computing resources or time.
import arrow.fx.coroutines.*
import kotlinx.coroutines.delay
class UserProcessor {
suspend fun start(): Unit { delay(750); println("Creating UserProcessor") }
fun shutdown(): Unit = println("Shutting down UserProcessor")
fun process(ds: DataSource): List<String> =
ds.users().map { "Processed $it" }
}
class DataSource {
suspend fun connect(): Unit { delay(1000); println("Connecting dataSource") }
fun users(): List<String> = listOf("User-1", "User-2", "User-3")
fun close(): Unit = println("Closed dataSource")
}
class Service(val db: DataSource, val userProcessor: UserProcessor) {
suspend fun processData(): List<String> = userProcessor.process(db)
}
//sampleStart
val userProcessor = resource {
UserProcessor().also { it.start() }
} release UserProcessor::shutdown
val dataSource = resource {
DataSource().also { it.connect() }
} release DataSource::close
suspend fun main(): Unit {
userProcessor.parZip(dataSource) { userProcessor, ds ->
Service(ds, userProcessor)
}.use { service -> service.processData() }
}
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