等待另一个未来结束以返回函数 [英] Waiting for another future to end to return a function

问题描述

假设我有一个函数func1，该函数需要返回带有两个整数的Future.这两个值中的每一个都是由独立的期货返回的，就像这样:

Let's say I have a function func1 that needs to return a Future with two integers. Each of the two values are returned by independent futures, like so:

def f1 = Future { 1 }
def f2 = Future { 2 }

def func1 : Future[(Int,Int)] = {

    val future1 = f1
    future1.map { result1 =>
       result1 * 10
    }

    val future2 = f2
    future2.map { result2 =>
       result2 * 20
    }

} 

我需要future1等待future2结束(反之亦然)，以将两个结果都作为(Int,Int)返回.如何做到这一点?

I need future1 wait until future2 ends (or vice versa) to return both results as (Int,Int). How can this be accomplished?

推荐答案

这正是期货zip方法的作用:

That's precisely what the zip method on futures does:

val futurePair: Future[(Int, Int)] = future1.zip(future2)

请注意，如果您之前未实例化期货(例如，如果future1和future2是def，而不是val)，则这将并行运行两个计算，而对于理解力(或flatMap)将等待第一个成功，然后再开始第二个.

Note that if you haven't instantiated your futures before (say, if future1 and future2 are defs, not vals), this will run the two computations in parallel, while a for comprehension (or flatMap) would wait for the first one to succeed before starting the second one.

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