Question

在promises上阅读此article，作者使用以下示例：

def redeemCampaignPledge(): Future[TaxCut] = {
    val p = Promise[TaxCut]()
    Future {
      println("Starting the new legislative period.")
      Thread.sleep(2000)
      //p.success(TaxCut(20))
      //println("We reduced the taxes! You must reelect us 2018!")
      p.failure(LameExcuse("global economy crisis"))
      println("We didn't fullfil our promises, so what?")
    }
    p.future
}

val taxCutF: Future[TaxCut] = redeemCampaignPledge()
  println("Now they're elected, let's see if they remember their promise.")
  taxCutF.onComplete {
    case Success(TaxCut(reduction)) =>
      println(s"Miracle! Taxes cut by $reduction percent.")
    case Failure(ex) =>
    println(s"They broke the promise again. Because of a ${ex.getMessage}")
  }

我的问题是，我不能摆脱Promise并将其重写为：

def redeem(): Future[TaxCut] = Future {
    println("Starting legislative period...!!!!")
    Thread.sleep(2000)

    println("We were successful")
    TaxCut(25)
}

第二个版本缺少什么？我并没有完全理解承诺带来的价值。

Answer 1

是的，你是绝对正确的。这是一个非常common anti pattern的JavaScript Promises（其中，Futures被称为Promises，Promises被称为延迟）。

基本上，它不是使用期货提供的延续，而是在像时尚这样的回调中围绕它们建立新的延续。

什么时候无法取代未来的承诺？

1 个答案: