在以下代码段中,调用getAmounts
以获取按货币分组的金额,然后调用getRates
以应用相应的汇率:
def getAmounts = Future(Map("EUR" -> 500d, "USD" -> 400d))
def getRates = Future(Map("EUR" -> 1d, "USD" -> 0.9))
getAmounts.flatMap { amounts =>
getRates.map { rates =>
amounts.foldLeft(0d)((total, amount) => total + (amount._2 * rates(amount._1)))
}
}.map { println(_) }
这是输出(500.0 * 1 + 400 * 0.9):
860.0
如何获得处理的金额(在这种情况下为2)?只有当两个Future
成功时,才应该增加计数。
答案 0 :(得分:1)
如何在Tuple2
中返回包含总数和计数的fold
:
amounts.foldLeft((0d, 0))
((accum, amount) => (accum._1 + (amount._2 * rates(amount._1)),accum._2 + 1))