Scala模式:对于产生未来的理解力[A] [英] Scala Pattern: For Comprehension that Yields a Future[A]

问题描述

Scala中用于处理场景的模式是什么?

What is the pattern used in Scala to deal with the scenario:

您有一堆期货(它们可以是任何东西，但是为了示例……)

You have a bunch of futures (they can be whatever, but for the sake of example...)

val aF = Future { true }
val bF = Future { Option(3) }
val cF = Future { myObject }

并且您有一些返回未来的函数

and you have some function that returns a future

def fooF: Future[SomeObject]

我想做类似的事情:

for {
    a <- aF
    b <- bF
    c <- cF
} yield {
    if (a) {
        // do stuff with b & c
        fooF
    } else {
        Future.successful(SomeObject)
    }
}

我想返回值Future[SomeObject]，但是我在yield语句中调用fooF时，我会得到一个Future[Future[SomeObject]]

I want to return a value of Future[SomeObject], but I call fooF inside of the yield statement, I will get a Future[Future[SomeObject]]

推荐答案

这是另一种解决方案:

def doStuffWith(a: A, b: B, c: C): Future[SomeObject] = if (a) {
  // do stuff with b & c
  fooF
} else Future.successful(SomeObject)

for {
  a <- aF
  b <- bF
  c <- cF
  d <- doStuffWith(a, b, c)
} yield d

正如@laughedelic答案中所讨论的，这是一个主观观点，但我认为这种方式更具可读性和可维护性(例如，始终删除该功能以对其进行单元测试).

As discussed in @laughedelic answer, this is a subjective view, but I believe this way to be more readable, and maintainable (taking out the function always to unit test it, for instance).

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