Scala 利用猫效应中的移位函数

我试图使用cats effect shift函数来异步运行代码

功能实现：

  def asyncSendMsg(producer: KkProducer)(record: KkRecord) : IO[Either[String, RecordMetadata]] =
    for {
      res <- trySendMsg(producer)(record).shift(BlockingFileIO).shift(Main)
    } yield(res)

  def trySendMsg(producer: KkProducer)(record: KkRecord): IO[Either[String, RecordMetadata]] =
    IO {
      try {
        Right(producer.send(record).get())
      } catch {
        case e: Exception => Left(e.getMessage())
      }
    }

def asyncSendMsg（生产者：kkkproducer）（记录：KkRecord）：IO[String，RecordMetadata]]=
为了{
res Left（如getMessage（））
}
}

尝试编译时，我收到：

[error] /home/developer/Desktop/scala/PureProducer/src/main/scala/TheProducer.scala:51:43: value shift is not a member of cats.effect.IO[Either[String,org.apache.kafka.clients.producer.RecordMetadata]]
[error]       res <- trySendMsg(producer)(record).shift(BlockingFileIO).shift(Main)
[error]                                           ^
[error] one error found
[error] (compile:compileIncremental) Compilation failed
[error] Total time: 2 s, completed Nov 13, 2017 2:18:06 PM

[error]/home/developer/Desktop/scala/PureProducer/src/main/scala/TheProducer.scala:51:43:value shift不是cats.effect.IO的成员[String，org.apache.kafka.clients.producer.RecordMetadata]]
[错误]res
IO.shift
是在
IO
的伴生对象上定义的（API在不同版本的CAT之间发生了更改），在调用IO调用之前，您可以使用它进行理解：

val nonBlockingExecContext = ExecutionContext.fromExecutor(Executors.newFixedThreadPool(10))

val res = for {
  _ <- IO { println(Thread.currentThread().getName) }
  _ <- IO.shift(nonBlockingExecContext)
  _ <- IO { println(Thread.currentThread().getName) }
} yield ()

res.unsafeRunSync()

@零编码当
unsafeRunSync（）
返回时，您回到
main
。并将另一个线程的计算值分配给主线程中的变量？@zero\u编码
unsafeRunSync
将执行此操作。
main
pool-1-thread-1