在以下代码段中调用getAmounts
以获取一些货币分组的金额,然后调用getRates
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
如何获得处理数量的数量(在这种情况下为2)?如果Future
S成功,应该增加计数。
如何在包含总计和计数的fold
中返回Tuple2
:
amounts.foldLeft((0d, 0))
((accum, amount) => (accum._1 + (amount._2 * rates(amount._1)),accum._2 + 1))