Resource
Computation block for the Resource type. The Resource allows us to describe resources as immutable values, and compose them together in simple ways. This way you can split the logic of what a Resource is and how it should be closed from how you use them.
Using and composing Resource
import arrow.fx.coroutines.continuations.resource
import arrow.fx.coroutines.release
class UserProcessor {
fun start(): Unit = println("Creating UserProcessor")
fun shutdown(): Unit = println("Shutting down UserProcessor")
fun process(ds: DataSource): List<String> =
ds.users().map { "Processed $it" }
}
class DataSource {
fun connect(): Unit = 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(UserProcessor::start)
} release UserProcessor::shutdown
val dataSource = resource {
DataSource().also { it.connect() }
} release DataSource::close
suspend fun main(): Unit {
resource<Service> {
Service(dataSource.bind(), userProcessor.bind())
}.use { service -> service.processData() }
}
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