获得任何一种的价值 [英] Getting Value of Either
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问题描述
除了使用match
之外,还有一种类似于Option的方式来getOrElse
的Right
或Left
值的实际内容吗?
Besides using match
, is there an Option-like way to getOrElse
the actual content of the Right
or Left
value?
scala> val x: Either[String,Int] = Right(5)
scala> val a: String = x match {
case Right(x) => x.toString
case Left(x) => "left"
}
a: String = 5
推荐答案
我不太喜欢Either
,因此我对它并不十分熟悉,但是我相信您正在寻找预测结果:either.left.getOrElse
或either.right.getOrElse
.
I don't particularly like Either
and as a result I'm not terribly familiar with it, but I believe you're looking for projections: either.left.getOrElse
or either.right.getOrElse
.
请注意,投影也可以用于理解中.这是直接来自文档的示例:
Note that projections can be used in for-comprehensions as well. This is an example straight from the documentation:
def interactWithDB(x: Query): Either[Exception, Result] =
try {
Right(getResultFromDatabase(x))
} catch {
case ex => Left(ex)
}
// this will only be executed if interactWithDB returns a Right
val report =
for (r <- interactWithDB(someQuery).right) yield generateReport(r)
if (report.isRight)
send(report)
else
log("report not generated, reason was " + report.left.get)
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