下面的代码是真实代码的简化版本。我们“继承了”我们无法修改的域模型case object FutTest
和case class FutTest
。实际的领域模型是从一个数据库提供的,所以我相信Future approach
是有效的,但它会导致我不明白的问题。Scala未来奇怪的编译错误
import org.scalatest.FunSpec
import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global
case object FutTest {
def create(sz: Int) = { FutTest(sz) }
}
case class FutTest(size: Int)
class FutureTest extends FunSpec {
def one(v: Int): Future[FutTest] = {
Future { FutTest.create(v) }
}
def two(t: FutTest) = {
Future { FutTest.create(t.size) }
}
def compileError1: Future[FutTest] = {
one(10).map(f => two(f))
}
def compileError2: Future[FutTest] = {
for { o <- one(10) } yield (two(o))
}
}
错误消息:
[INFO] Using incremental compilation
[INFO] Compiling 7 Scala sources and 5 .. target/test-classes...
[ERROR] domain.FutureTest.scala:25: type mismatch;
found : scala.concurrent.Future[domain.FutTest]
required: domain.FutTest
[ERROR] one(10).map(f => two(f))
[ERROR] ^
[ERROR] domain/FutureTest.scala:29: type mismatch;
found : scala.concurrent.Future[domain.FutTest]
required: domain.FutTest
[ERROR] for { o <- one(10) } yield (two(o))
我试图用普通Int
代替FutTest
上面的代码和所有的罚款。为什么编译器会抱怨,我们如何解决这个问题,而无需触及现有的域。
我不相信这个,如果你更换'和'Int' FutTest'工作。 –