scala 我怎样才能将未来的未来变成一个未来的对象？
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How can I make A future of future into one future object?
提问by Vincent Zou
Env: Akka 2.1, scala version 2.10.M6, JDK 1.7,u5
环境：Akka 2.1，scala 版本 2.10.M6，JDK 1.7，u5
Now is my problem: I have:
现在是我的问题：我有：
future1 = Futures.future(new Callable<Future<object>>(){...});
future2 = ? extends Object;
Future.sequence(future1, future2).onComplete(...)
now in first line, I have a future of Future of object, is there any way to convert it into a Future while not blocking my current thread?
现在在第一行，我有一个 Future of object 的未来，有什么方法可以将它转换为 Future 而不阻塞我当前的线程？
Is there any method in akka? As far as I checked, I havn't found any yet... First time to have a post....Sry for bad format and organize... :~P
akka 有什么方法吗？据我检查，我还没有找到任何东西...第一次发帖....Sry格式错误并组织... :~P
回答by Viktor Klang
Short answer (English): flatMap dat sh!t
简答（英文）： flatMap dat sh!t
Shorter answer (Scala):
更简短的答案（Scala）：
flatMap(identity)
Shortest answer: (Scala 2.12):
最短的答案：（Scala 2.12）：
flatten
Long answer (Java):
长答案（Java）：
flatMap(new Mapper<Future<X>>,Future<X>>() {
@Override public Future<X> apply(final Future<X> f) { return f; }
})
回答by VonC
Note: Since Viktor Klang's 2012 answer, he recently (March 2016) added in his blogfor scala 2.12:
注意：自从Viktor Klang的 2012 年回答以来，他最近（2016 年 3 月）在他的博客中为scala 2.12添加了：
Missing canonical combinators: flatten
缺少规范组合器： flatten
Are you one of us
Future-users who have grown tired of the oldflatMap(identity)boilerplate for un-nesting Futures as in:
您是我们中的一员
Future吗 - 已经厌倦flatMap(identity)了取消嵌套 Futures的旧样板的用户，例如：
val future: Future[Future[X]] = ???
val flattenedFuture /*: Future[X] */ = future.flatMap(identity)
Then I have some great news for you! Starting with Scala 2.12
scala.concurrent.Futurewill have a flatten-method with the following signature:
那么我有一个好消息要告诉你！从 Scala 2.12 开始，
scala.concurrent.Future将有一个带有以下签名的 flatten 方法：
def flatten[S](implicit ev: T <:< Future[S]): Future[S]
Allowing you to write:
允许你写：
val future: Future[Future[X]] = ???
val flattenedFuture /*: Future[X] */ = future.flatten
回答by Peter Lawrey
You can create another task
您可以创建另一个任务
Futures.future(new Runnable(){
// wait for future1
// wait for future2
// do something with the results.
});
or merge the tasks
或合并任务
Futures.future(new Runnable(){
// do the work future2 would have done.
// wait for future1
// do something with the results.
});
