我如何使用ifguard进行理解?
type Error = String
type Success = String
def csrfValidation(session:Session, body:JsValue):Either[Error,Success] = {
val csrfRet = for (csrfSession <- csrfStateSessionValidation(session).right;
csrfReq <- csrfStateReqBodyValidation(body).right if (csrfSession == csrfReq)) yield (csrfReq)
if (csrfRet.isRight)
Right(csrfRet)
else {
Logger.warn("request and session csrf is not the same")
Left("Oops,something went wrong, request and session csrf is not the same")
}
}
使用时出现此错误。
'withFilter' method does not yet exist on scala.util.Either.RightProjection[Error,Success], using `filter' method instead
编辑:
我又遇到一个错误。我认为如果使用防护罩,它将返回选项结果。
[error] type mismatch;
[error] found : Option[scala.util.Either[Nothing,controllers.ProfileApiV1.Success]]
[error] required: scala.util.Either[?,?]
[error] csrfReq <- csrfStateReqBodyValidation(body).right if (csrfSession == csrfReq)) yield (csrfReq)
编辑2
This is what I did to fix above error. I also move if-guard to later process.
val result = for {
foo <- Right[String,String]("teststring").right
bar <- Right[String,String]("teststring").right
} yield (foo, bar)
result fold (
ex => Left("Operation failed with " + ex),
v => v match {
case (x,y) =>
if (x == y) Right(x)
else Left("value is different")
}
)
最佳答案
我相信您看到的是编译器警告,而不是实际错误。 RightProjection
不支持withFilter
,这是保护条件的“首选”(但不是必需的),因此改用普通的filter
。关于这些功能的差异以及产生原因的原因,请查看下面的链接以获取解释。
http://scala-programming-language.1934581.n4.nabble.com/Rethinking-filter-td2009215.html#a2009218