Question

在Scala中，我想定义一个Trait，用于在单独的Thread中执行某些代码，如下所示：

val value = RunFuture {
    // hard work to compute value...
}
// This was not blocking, so I can do
// some other work until value is computed...
// Eventually, I can use
value.getResult

我写了这个：

object RunFuture
{
    def apply[A](block : => A): Future[A] =
    {
        val future : Future[A] = new Future[A]
        val thread : Thread = new Thread {
            override def run {
                future.result = block
                future.done = true
            }
        }
        thread.run
        return future
    }
}

trait Future[A]
{
    var done : Boolean = false
    var result : A

    def getResult() : A = {
        if (done)
            result
        else
            throw new Exception("Wait for it!")
    }

    def waitForIt() : A = {
        while (!done) {
            // wait...
        }
        result
    }
}

但是这不会编译，因为trait Future is abstract; cannot be instantiated

如果我尝试像这样实例化它：

val future : Future[A] = new Future[A] {}

而不是

val future : Future[A] = new Future[A]

...当然，编译器会告诉我object creation impossible, since variable result in trait Future of type A is not defined

但是，结果的类型未知。我不能写

result = null

因为这会导致type mismatch;

如何解决这个问题？

使用并发变量赋值实例化通用Trait

0 个答案: