stateless-future异步编程 Future
stateless-future 用于异步编程的纯函数风格Future
示例代码：
import scala.concurrent.duration._
import scala.util.control.Exception.Catcher
import com.qifun.statelessFuture.Future
val executor = java.util.concurrent.Executors.newSingleThreadScheduledExecutor
// Manually implements a stateless future, which is the asynchronous version of `Thread.sleep()`
def asyncSleep(duration: Duration) = new Future[Unit] {
import scala.util.control.TailCalls._
def onComplete(handler: Unit => TailRec[Unit])(implicit catcher: Catcher[TailRec[Unit]]) = {
executor.schedule(new Runnable {
def run() {
handler().result
}
}, duration.length, duration.unit)
done()
}
}
// Without the keyword `new`, you have the magic version of `Future` constructor,
// which enables the magic postfix `await`.
val sleep10seconds = Future {
var i = 0
while (i < 10) {
println(s"I have sleeped $i times.")
// The magic postfix `await` invokes the asynchronous method `asyncSleep`.
// It looks like normal `Thread.sleep()`, but does not block any thread.
asyncSleep(1.seconds).await
i += 1
}
i
}
// When `sleep10seconds` is running, it could report failures to this catcher
implicit def catcher: Catcher[Unit] = {
case e: Exception => {
println("An exception occured when I was sleeping: " + e.getMessage)
}
}
// A stateless future instance is lazy, only evaluating when you query it.
println("Before the evaluation of the stateless future `sleep10seconds`.")
for (total <- sleep10seconds) {
println("After the evaluation of the stateless future `sleep10seconds`.")
println(s"I sleeped $total times in total.")
executor.shutdown()
}
输出结果：
Before evaluation of the stateless future `sleep10seconds`. I have sleeped 0 times. I have sleeped 1 times. I have sleeped 2 times. I have sleeped 3 times. I have sleeped 4 times. I have sleeped 5 times. I have sleeped 6 times. I have sleeped 7 times. I have sleeped 8 times. I have sleeped 9 times. After evaluation of the stateless future `sleep10seconds`. I sleeped 10 times in total.
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