arrow-fx-coroutines/arrow.fx.coroutines/Resource/parZip

parZip

fun <B, C> ~~parZip~~(fb: Resource<B>, f: suspend (A, B) -> C): Resource<C>

Deprecated

parZip is redundant and will be removed in Arrow 2.x.x in favor of the DSL. In case you think this method should stay, please provide feedback and your use-case on https://github.com/arrow-kt/arrow/issues

Replace with

import arrow.fx.coroutines.resource

resource { parZip<A, B, C>({ this.bind() }, { fb.bind() }) { a, b -> f(a, b) } }

fun <B, C> ~~parZip~~(ctx: CoroutineContext = Dispatchers.Default, fb: Resource<B>, f: suspend (A, B) -> C): Resource<C>

Deprecated

Replace with

import arrow.fx.coroutines.resource

resource { parZip<A, B, C>(ctx, { this.bind() }, { fb.bind() }) { a, b -> f(a, b) } }

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)
}

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() }
}